Project car - 1989 75 3.0 V6 [Updated 12 November 2021]

[Hudders]

Brilliant thread and a brilliant resource for people restoring these great cars.
Many thanks for putting so much detail into of your posts and your photography puts the rest of us to shame.

I found this thread while trying to get details of the underside of a 75 and I found it surprisingly difficult.
This thread is a lifesaver.

I'm doing up a twin spark LE at the moment and trying to keep it factory.
Unfortunately it's in a lot worse shape than yours and I'm certainly not the first person to work on it so a lot of bodges had to be removed and I've no idea of how many of the original details were e.g. pipe runs etc.

If anyone's interested my efforts are on the UK website "Mig welding forum"
https://www.mig-welding.co.uk/forum/threads/25-year-old-alfa-75-back-from-the-brink-hopefully.81348/

admin, feel free to delete the link if it's not allowed

Thanks again

As a fellow 75 owner from England, I will be following your build with interest, my 75 has rust, how much I as yet don't know but what I do know is it is certainly more than the tiny little scabs on Shiny's, not jealous about dry Australian cars at all, lol.

[arristoss]

Hello to everyone. Can anyne tell me where i can find those strange switch bulb holders as shown in the page 22?

[shiny_car]

Hello to everyone. Can anyne tell me where i can find those strange switch bulb holders as shown in the page 22?

I doubt that you can buy new-unused original ones separately. Probably best to buy a used switch that includes the bulb holder.

[shiny_car]

Hello again!

Wow, it's been 5 years since I posted any work on the car.  And unfortunately, during this time I have not made opportunity to continue.  But now, after years of wanting to, pondering, wishing I made time, what was 2020  ...I have redeveloped the passion to recommence!

Because it's been 5 years, I've had to relearn everything I knew about 75's, by reading scores of forum topics (here, including readings this very topic (!), AlfaBB.com, elsewhere), rummaging through my old notes, creating a full inventory of all my parts, and refreshing the overall plan.  Though, I've learnt many new things along the way, and through research, I've decided to take the car to another level. 

The major difference to my initial dream - now 10 years ago when I bought the car! - is to go the full hog with the engine, and go with programmable fuel injection.  I'm yet to finalise any details; and work on this particular development may be a year away after I complete many other things, but my plan includes:
- programmable system, likely Autronic, if I purchase from Beninca Motors and utilise their skills and advice to make it happen
- this means ditch the airflow meter, and go with MAP (manifold absolute pressure) / IAT (intake air temperature) / CTS (coolant temp sensor) / crank pulley timing wheel and VR (variable reluctor) sensor / potentiometer TPS (throttle position sensor); I've already made some inroads with some of the gear
- COPs (coil on plug) ignition, and ditch the distributor and high tension wires
- yet to decide whether I want any, or combination of, wide band Lambda/O2 sensor and AFR (air fuel ratio) meter, EGT (exhaust gas temp), fuel pressure sensor, knock sensors; I don't believe any of these will add to the day-to-day performance once the car is properly tuned, but I might add a batch of gauges in the interior
- cams: I've ordered a set of RJ (Richard Jemison, who is a regular on AlfaBB.com forums) cams from the US, and decided on a high performance 'street' cam that optimises both torque and power for the road
- very minor head clean-up / porting, which I presume Beninca can perform
- largely a complete engine rebuild, with 10:1 CR (compression ratio) pistons (as fitted to the Potenziata)

Of course, that means an engine-out job, but I'm also motivated by needing to replace the leaking rear main seal.  So whilst I'm there... 

For this return-post, I'm showing just some of the parts that I've bought, much of it very recently:

Though, firstly, this is the Evolutione bodykit that I bought from JOHN G (you in Oz at the moment mate?!).  From what I can tell and recall, it's the real deal, or at least it's a very high quality kit.  I never did ask where he got it from originally.  Compared with the flimsy stuff that I contemplated repairing and fitting (ie: the pieces that used to belong to jazig.k; I posted some pics of these on Oct 06 2013), this kit is very solid, and thus relatively heavy despite being fibreglass.  Some minor repairs are required for the front bumper 'slats' where it's cracked, but nothing major.















BMC CDA (Carbon Dynamic Airbox) and aftermarket 75/SZ-specific parallel-flow aircon condenser.  Not everyone approves of custom air intakes and filters, but some seem better than others; because this setup is fully enclosed, I can create some form of cold air intake.



Now onto some more serious stuff, the full RSR (Ron Simons Racing) adjustable suspension setup.  From the decals, you can see it's built by Intrax; the Intrax catalogue lists its own large range of suspension setups for this car (including far more serious racing upgrades), but this is one of the sets designed/tuned to Ron Simons's specs.  Of the two kits he created, this is the adjustable-shock absorber version (for combined compression + rebound); having fitted various suspension parts to my cars over the years, I've always found any non-adjustable setup to be a little lacking, so I am happy to stump up the extra for some fine tuning ability.

The kits are available directly through RSR (I'm speculating/observing here, but I think Ron Simons was bought-out by another company but they still utilise the name): https://www.trackmodified.com/product/alfa-romeo/

However, I bought from OKP in Germany, who sell the kit, and held an Easter sale: https://www.okp.de/xtc2/

After researching what suspension options were available, I determined that the RSR kit had very favourable feedback from users, provides a very complete setup, and is readily available.  There's undoubtedly cheaper setups, and possibly 'better' setups (though that may be subjective), but this has always been my dream kit.  So here it is.



Front coilover: this works with the original torsion bars (ie: doesn't replace them), and provides the adjustable shock absorber, and adds another spring for increased spring rate.  The thin red spring is a 'helper spring' to keep the main spring in position during full extension.  The threaded adjustable platform can alter tension, but mostly caters for whatever ride height you choose (ie: after setting the ride height via the torsion bars, you can then dial-in the coil spring tension).  The black, knurled knob near the bottom bracket twists, to make the compression/rebound adjustment.





Rear springs sit on adjustable platforms to alter ride height.





Rear springs and shocks fit in the standard location points.  Shocks adjustable from the top.





Front antiroll bar seems a crazy 30mm diameter!  Maybe it's rubber  except it's quite heavy, so I figure it's steel.  Rose/rod-end/heim joints affix the ends to the lower suspension arms.  I will add rubber boots to cover the joints and keep them clean, and I have reinforcement plates that need welding to the chassis where the bar is bolted in place.



Rear antiroll bar is 26mm diameter, and adjustable via the different attachment holes.  Rather fancy looking billet 'brackets' attach to the original De Dion mounts.



To round out the suspension, I have the Watt linkage parts (it's part of the package, but I bought it separately years ago when someone in the UK was selling it, unused), and De Dion spherical bearing.





Next: these parts are from Chris Snowdon Racing (operated by Richard Melvin, an experienced UK campaigner).  Richard is great to deal with, and some of the racing parts on offer are quite serious but unfortunately go beyond what even I consider appropriate for a street car (yes, some of my parts might not have ADR certification, but I think an engineer might find they would meet the standard if required...maybe!).

https://alfettagtv6.co.uk/



For the front suspension, these are extended-pin upper ball joints, the sealed version (ie: feature the metal cap + rubber boot for protection).  Some of you may use knuckle-risers, which achieve the same outcome, to raise the end of the upper suspension arm into a more favourable position (for better camber during cornering).





This is a reinforced clutch housing.  I probably don't need it, but hey, why not?!  If I achieve 250-260 hp (~190kW) from the engine I'll be happy, but that still probably wouldn't crack the original housing; not from driving on the street.  But this is something fancy!





And a few extra bits and pieces.  Here is a crankshaft pulley from a 164 featuring a '60-2' toothed timing wheel.  Apparently this can be pressed-off, then the 75's pulley needs some minor machining (to make slightly smaller diameter), before being pressed onto it.  It's seemingly impossible to find an original Potenziata pulley with the wheel, but one advantage of keeping my original pulley is that it's already balanced with the crankshaft and flywheel, so the toothed wheel shouldn't impact in that regard.  'Timing' is achieved with a VR (variable reluctor) sensor that is 'in the post', but I also have an original mounting bracket.  And because the timing wheel creates a bigger overall diameter pulley, this fouls against a standard water pump pulley; hence, the need to change to a Potenziata setup, which means a water pump shown here, that uses a separate smaller diameter bolt-on pulley...that's 'in the post'  .  I hope it fits!





Lastly, an LSD upgrade kit, from Racing Diffs.  This will refurbish the factory diff, but with 4 friction plates instead of 2.  Nice, complete kit from the looks.

https://www.racingdiffs.com/products/alfa-romeo-lsd-clutch-kit





It's nice to be back - posting - and of course getting my hands dirty again.  I don't know whether I'll be posting every month like before, but I'll post when there's a worthwhile update on progress.

Thanks for looking...again. 

[GTVeloce]

Great to see you back posting and with such shiny parts! Serious part envy here.

Although, no electric water pump? 

[shiny_car]

Although, no electric water pump? 

Hmmm *strokes chin*. 

[shiny_car]

I've pleasingly made time to work on the car, so there's been some good progress, and new parts continue to make their way from various parts of the world onto my shelves.

I spent my first session removing the transaxle from the vehicle.  That was quite straight forward.  Then spent the next group of days stripping it.  Some of that wasn't so straight forward!

Part 1

Firstly, the front wheels were chocked, and then the rear was raised onto axle stands.  Silver stands support the vehicle by the jack points; red stands are holding the De Dion tube for the moment, but not taking the weight of the whole vehicle.  I gave the floor underneath a good vacuum and clean.



To summarise transaxle removal:
1. disconnect the minor parts: antiroll bar, shock absorbers, brake line, speed sensor, reverse gear switch, clutch line, gearshift rod, prop shaft (I'd already done this), exhaust
*coffee time*
2. disconnect the major parts: front crossmember, Watt's linkage arms, gearbox rear connection
*have another coffee*

The antiroll bar and shock absorbers were unbolted.





Shock absorbers attach to the De Dion infront of the rear wheels.  They also limit suspension travel, as I discovered; the wheels will drop to the ground if unsupported!  Hence, the axle stands under the De Dion tube were important.





Rear brake hose and handbrake cable were detached.



To prevent brake fluid from completely draining out, I wanted to leave the flexible hose connected to the hard line (pipe), and clamp the hose (which will be replaced, so no issues if it is deformed from the clamp).  However, to disconnect the far end from the T-junction, the whole hose needed to twist to unscrew, so the hose needed to be unfastened from the hard line first.  The connection between hard line and flexible hose was supported by a chassis bracket.  Handbrake cable nuts then loosened and removed from the caliper arms.





On the left side of the gearbox, the speed sensor was removed, and reverse-gear switch unscrewed.  A while ago I temporarily loosened the speed sensor and did not refit it completely, hence oil has seeped out.  The oil stains are not from leaks elsewhere!  I tucked the sensor and switch over the handbrake cable, out of the way.





Then on the right side, the hose was removed from the clutch slave cylinder.  Like the brakes, the hose needed disconnection from the hard line first, then unscrewing from the cylinder.





At the front, the gearshift rod was detached from the gearbox linkage.  The rod was cleaned and painted previously, which is why it looks clean.  Back then the roll pin had been partially reinserted (hence it's sticking out of the rod, in the photo); I couldn't pull it out easily, so had to punch it right through, and out the other side.  Prop shaft previously removed (years ago).



Last minor task, to disconnect the exhaust centre section from the rear muffler.  After loosening the clamp, the slip joint seemed seized.  The centre section is to be replaced, so I started attacking it with a reciprocal saw, only for the joint to fall apart before I'd finished!





I kept a couple pallets to hold and manoeuvre the transaxle.  I initially secured swivel wheels to the larger pallet, but then realised the smaller one was more suitable because it could fit between the car wheels.



To fit the pallet under the car, and the trolley jack beside it, I swapped-out the red axle stands supporting the De Dion tube for blocks of wood under the wheels.





The six bolts holding the front crossmember were removed (2 short, 4 long), and then lowered onto the pallet.





The Watt's Linkage arms were unbolted from the chassis.





The last disconnection point was the gearbox rear mount.  The gearbox was obviously heavy, so required support from underneath (with blocks of wood) to remove the bolt easily, before gently lowering onto the pallet.  I removed the rear muffler to make the job easier.







With the wheels removed, the whole transaxle could be rolled out. Yeh!  The springs were also wiggled out from their positions without difficulty.





/Part 1

[shiny_car]

Part 2

The transaxle was 'parked' to one side in my garage until my next session, to dismantle it into sections.



Off came the Watt's Linkage from the centre pin.  Bit of surface rust on the pin.







The wheel shaft was secured by a large nut, covered by a lock nut secured by a split pin.  After straightening the arms, the pin did not slip or punch out easily, hence quicker to cut the arms off first.  The lock nut simply fitted loosely over the main nut.









Temporarily refitting the wheels made it easier to 'break' the axle shaft bolts loose.  The axles then slipped out of position.





The inboard rear brake discs were bolted to the diff shafts via a spacer.  To break these bolts loose, I engaged the 'handbrake' to hold the discs stationary, using a turnbuckle and shackle I had lying around.





Pads were removed, allowing the discs to drop out.  Keep hold of the pad anti rattle clip when taking out a retaining pin, or else it will spring out...and hit you in the face (don't ask how I know).







Brake fluid hard lines were removed.  The T-piece bolted to the gearbox, and a bracket held the righthand pipe.





Brake calipers removed from their studs.  Some surface rust on the left studs.







Clutch slave cylinder slotted through a hole, and held by circlips either side.

The rubber boot was secured by cable ties.  It appeared to be cut along the inside, presumably by a 'lazy' mechanic who didn't want to remove the slave cylinder to slide the boot into position intact.





Unsurprisingly, the push rod and clutch fork were grubbier than they could have been.



Slave and clutch fork removed.







These were the chunky metal spacers that fit between the crossmember and chassis.  Their thickness on the 75 is apparently more than the GTV or Alfetta sedan.



Isostatic gearshift linkage!  Some people loathe it because the shift quality suffers when the components wear.  It does seem overly complex.  I will completely overhaul it with new aftermarket parts.  Schematic might add clarity:



Moving the gearstick fore and aft (blue arrow; eg: changing from 1st to 2nd gear) naturally moves the gearbox shift rod in and out.  Moving the gearstick side to side (eg: across from 1st/2nd to 3rd/4th row) rotates the shift rod via the Isostatic linkage (red arrows). 



The 'engagement lever' (#5 in schematic) pivots at this neat little rod end bearing.



The linkage bolted to this arm on the end of the shift rod.  I found a fair amount of (abnormal) free-play between the arm and rod.  A roll pin secured the arm in position.

[shiny_car]

A separate bracket, bolted to the left side gearbox mount, held the Isostatic linkage.  The M6 bolt passed through the mount (red arrow) then a spacer and out the other side of the bracket.



Gearbox mounts removed, now freeing the gearbox from the suspension completely.





Around the back again: I temporarily refitted the wheel to hold the hub still, to remove the main nut.  I could not break the nut free with the wrench I had (torqued to 265-324 Nm when fitted), so out came the air impact wrench.  Tightness and rust meant it still took some effort, and penetrating oil, to be removed.

The wheel shaft was easily pushed out with a whack from a hammer.





But, oh, to remove the hub!!  I'd read about this job being one of the most difficult on the whole car, because parts seize together.  I didn't anticipate this to be such an issue on an Australian car, compared with a vehicle in the UK driven on salted roads.

The common problem is the hub (green arrows) seizing to the bearing (red arrows).  The problem is more difficult because of the factory 'dust shield' fitted to the hub, which prevents tools from being used in that area (eg: to slot a bearing remover into the gap, or attach the claws of a gear puller around the De Dion).



The whole De Dion and hub don't fit at the correct angle in a standard hydraulic press (I tried!).  I also tried a 'big hammer' to punch it out (with thanks to my patient wife, who held the De Dion upright without dropping it); fail.  Then I refitted it to the axles and gearbox to brace the wheel shaft, but there was too much slack in the CV joints to brace the shaft adequately. FAIL.

I was a little disheartened.  I didn't really need to pull this section apart because the bearings felt quite smooth.  But having it in pieces would make cleaning and painting easier.  After using the big hammer, I must have damaged the bearing a little, because it was now rough and a bit sloppy.  So then I was forced to finish the job.

Look at the factory tool to brace the back of the wheel shaft!  I don't have one of these in my toolbox. 
(Images courtesy of: http://www.dep-o.co.uk/features/replacing-alfetta-rear-wheel-bearing/)





The wheel shaft requires 'fixing' in position to use tools to pull the hub out.  I did more research, and saw many home made tools and mash-up tools to replicate the factory version.  Hoping not to spend more $$ on more equipment, I chanced upon a technique using the opposite wheel shaft as a brace.  Voila, it worked!

With the shaft braced, I could use a conventional gear puller to grasp the hub, and push against the end of the shaft.  Together with lots more penetrating oil sprayed onto the bearing/hub, a big hammer intermittently whacking the tip of the gear puller, and poking my tongue in a south easterly direction (!), the hub went TWANG and it shifted!  I gradually 'wound' it out, twang by twang.





The rear wheel bearing is a 'double row' bearing (two bearings side-by-side in one housing).  The wheel hub was successfully pulled from the inside bearing, but the outside half remained stuck to the hub.  I'd seen many photos of the same situation.  Removing the outer half is a job for the future, but shouldn't be too bad.



The remaining parts of the bearing were the outer race and inside bearing.  And clumps of old grease; bearing probably due for replacement anyway.



Surely the left hub would be easy enough, having won the battle on the right.  No!  The rusty discolouration was perhaps a clue that it was more seized.  Aside from penetrating oil, this one required fire!  Out came the propane torch.  I focused on heating the bearing, theoretically causing it to expand and loosen from the hub; but of course, heating the hub was unavoidable.

The twang when the hub first shifted was again startling!









The bearings were secured in the De Dion by a thin retaining 'nut' (red arrows).  This was revealed after cleaning away the grime.  The nut will also be replaced, thus suitable to cut out.  After carefully cutting through a couple places, a segment was bent up, and then easily pulled out.





Removing the remnants of the bearings was not difficult, with tools I already had.  These included a set of drifts of various diameters (eBay: sold as Bearing Seal Drive Tool Kit), a large ball joint remover (glorified G-clamp, with its own set of drifts), and gear puller.

Starting with the ball joint remover and 64mm diameter drift, removal was initiated.  Once broken free, I used the puller to...err, push.  The claws had to be positioned out of the way.  Hmm, this step felt like it was giving birth to a bearing!  Puuuushhh, harder!  Here it comes!  Pop.









Right then left sides completed.





Lastly, unbolted the front of the De Dion triangle from the crossmember.  I manoeuvred the triangle from under the gearbox and flipped it over, to access the bolt head.





This came apart easily.  The bush looked in good shape, but will be replaced by a spherical bearing.

The silver 'washer' was the original spacer.  However, sandwiched between the spacer and bush, I found what looked like an exhaust hanger.  This isn't a standard inclusion according to the Workshop Manual and ePer parts list!  I'm guessing it was fitted either as a dust seal or to reduce some clunking noise.





There were two spacer rings, above and below the bush, to help hold it in position.



All done for now - tucked away again. Everything is ready to be cleaned, repainted, replaced, and/or fixed.  I'll clean the outside of the gearbox, then access the clutch, and crack open the 'box to change some internal parts including the synchros.



/Part 2

[shiny_car]

Part 3

Here's a selection of more replacement parts that have arrived.  Anything and everything that can potentially be upgraded, or replaced, has been researched, considered, and sourced accordingly.  Parts have come from overseas, including the US, UK, Germany, and Italy.

CSC stainless centre exhaust section.  I thought CSC Marmitte had closed shop permanently; I read they have filed for bankruptcy three times in the past, probably four.  EB Spares supplied this, so I presume they are back in business!



This little kit from AHM, replaces the distributor with a mini shaft, bearing, and cap.

https://www.ahmotorsports.co.uk/



The water pump I originally purchased via eBay, perhaps unsurprisingly, did not fit the Potenziata pulley I bought separately.  Many internet stories about difficulty finding a water pump with the correct (small) size mounting plate that suits.  The pump I received - despite being advertised as suitable - was really a 164 pump, with larger flange.  One day I might find the right pump!





Instead, EB Spares sell this replica SZ/RZ water pump that should work.  The pulley on either setup is meant to clear the trigger wheel fitted to the crank pulley on Motronic engines, whereas the L-Jet V6 pulley dose not.  So hopefully this works!



Brise make smaller (lighter and more powerful) starter motors that are a bolt-on replacement.  This is necessary (perhaps not essential) with CSC exhaust headers fitted, which reduce the clearance with the original starter.

https://brise.co.uk/







Rear brake caliper spacer kit, modifies the calipers to accept ventilated discs.  Several vendors offer similar.  This kit is from CSR (Chris Snowden Racing), where I also purchased the front extended-pin upper ball joints and reinforced clutch housing, that I posted about last time.  The kit includes the spacers, O-ring seals, longer bolts, and longer pins.





This kit might interest some of you.  I saw it on a facebook post!  Alfonso Ciardullo, from the US, makes a mounting plate to hold a bearing for a longer cam belt that provides far more wrap around the pulley.  The kit includes all required parts, and is a direct bolt-on (except requires a small amount of the head to be ground flat near one bolt hole); the belt is a Toyota Cressida part, and bearing from a Lexus.  It was US$450 + shipping.  He has used and refined the setup in his race cars over many years, apparently without any issues.



One of Alfonso's FB photos:



Message me if interested in contacting him.

/Part 3

That's it for this month.  Thanks for looking!
Richard

[alfagtv85]

Shiny

I have been following your post from the beginning and am really glad that you are back and working on the 75, your attention to detail is incredible and the pictures are both fantastic and informative, especially to someone who is not mechanically talented.

I use the information that you provide to work on my 75, although not to the extent that you do.

I love what you do, keep it going!

[shiny_car]

@ alfagtv85: thanks mate!  I'm glad it's of help, and hopefully demonstrate that it isn't too hard to do all these things.  I'm not trained in mechanics or engineering, just a backyard enthusiast, so if I can do it, so can others.

Part 1

Hello again!

Carrying-on from last month, I removed the bush from the De Dion.  I flattened the stakes back, using a hammer and punch; enough to free the metal retainer ring.  Then supported the whole triangle under my hydraulic press, and pushed the old bush out using a 54mm diameter drift.  The workshop manual refers to upper and lower retaining rings, but my car only had one.







De Dion then put aside for future cleaning and painting.

Next, I cleaned most of the gearbox and split it open (something I'd never done before, so kinda fun).  It was amazing how clean some of the parts were underneath all the grime.

I drained any remaining oil from the 'box, by removing the drain plug and tilting on its side, emptying into an old container.  Obviously the oil will still drain without tilting (ie: when the gearbox is still on the car).





The 'box was quite filthy on the outside; a mix of oil, dirt, and debris:





I used an old wire brush to remove the loose crud initially:



The differential end was quite oily, so I resorted to degreaser and a high pressure hose.  Before the degrease:



After the degrease, and drying, I attacked the surface with a combination of stainless steel wire brushes, including a coarse brush on a drill, and Dremel attachments, combined with Wax & Grease Remover and rags:



Bottom half mostly done, top half still to do:



After what I guess as about 8 hours of cleaning across a few days, I was very happy with the result.  The diff housing was the most time-consuming.  I will still do a final wipe-down after the box is stripped and reassembled, before refitting to the car.  I've read and seen pics of other peoples' housings after bead/particulate blasting and/or chemical cleaning, which can look fantastic, but I still really like the finish I've achieved.











On the underside was what appeared to be a serial number.  And on the side was probably the month of manufacture: '4 dots' in the '8' quadrant which I presume means April 1988.





Under all the grime, I found the gearbox ventilation tube.  This equilibrates pressure inside the 'box when it heats and cools; excessive internal air pressure can cause oil leaks past the seals.  No idea if mine was effective, because it appeared so clogged on the outside.  Spot it here in one of my previous pics:



And here after cleaning the exterior of the gearbox:



From research, I determined it was press-fitted into the casing.  So I used an old, cheap quality 'ball joint separator' to drive as a wedge (RED arrow) between two spanners, to push the vent up and off.







Inside the vent was material like wire wool, sandwiched between two wire mesh openings.  I soaked it in wax & grease remover, then blew compressed air in both directions.





Cleaned and functional again!  Then put aside to refit later.

[shiny_car]

Part 2

Back around the clutch end of the gearbox: I loosened the double-nuts with my air impact wrench, and checked the prop shaft fork would be easy to remove using a puller (it wasn't seized).  Four bolts secured the clutch housing to the gearbox, and it was easily separated.







With the clutch removed, revealed was the:
- hollow thrust bearing support tube (the clutch thrust bearing slides along the tube (RED arrow) to engage/disengage the clutch; the main gear shaft rotates inside the tube and connects to the clutch)
- clutch fork pivot bolt, also shown (second pic) through the opening where the fork passed into the clutch housing





Thrust bearing support tube removed:



Two oil seals to be replaced later:
- main input shaft
- shift rod



Back to the other end, for the diff: cut-outs in the diff axles provided access to four Allen head bolts each side, securing the axle flanges to the casing.  The flanges were sealed to the casing, though mine were easy enough to remove; there were thin recessed gaps behind each bolt 'ear', where a cold chisel could be GENTLY tapped, to separate the parts.







Left and right diff axles: note their different lengths.  Later, I will dismantle the axles and flanges to change the oil seals.



12 bolts secured the diff cover to the main casing.  Easy to remove; I found no sealant here, but I will apply some on reassembly.  Note the 'oil level' mark: the clean area had been bathed in gearbox oil, and the darker area was stained by 'dirty' splashed oil (? containing metallic wear particles from gears, synchros, etc).



The diff carrier (ie: differential housed inside) with 39-tooth ring gear and bearings, just slipped out once axles removed.



Now viewed inside the casing were the:
- 11-tooth pinion gear (this equates to a 39/11 = 3.55 diff ratio; later Potenziata/QV cars have a shorter (41/11) 3.73 ratio, and 4 cylinder cars have an even shorter (41/10) 4.10 ratio)
- end of the main gear shaft and its bearing
- ends of the gear selection shift rods that slide in/out
- oil drain plug that I removed for the photo



To split open the gearbox, the bolts and nuts were removed.  Some were relatively flush with the casing, preventing the head of a ratchet-drive fitting directly into position, so a universal joint was handy.  The clutch slave cylinder mounting bracket was removed with three of the bolts.





The gearbox casings were sealed together, and required a few whacks from a mallet via some hardwood timber offcuts (RED arrow).  The workshop manual refers to three main sections for the gearbox:
1. clutch-speed casing (the forward section housing the clutch and some of the gears
2. intermediate flange (thin mid section that supports the gear shafts and shift rods)
3. diff-speed casing (the rear section housing the differential and some of the gears)



The mallet successfully split the gearbox into the three sections.  Here, I started by removing the clutch-speed casing.  In doing so, the reverse 'idler' gear slipped off its short support shaft (expected).



There were only two major gear shafts:
1. main input shaft (rotates in direction of engine crankshaft (RED arrow))
2. pinion shaft (rotates in opposite direction (RED arrow))

Connection of the two shafts via the (1st to 5th) speed gears generates forward motion of the car, so naturally there must be the additional reverse 'idler' gear between the two shafts when Reverse is selected, so that the pinion shaft rotates in the SAME direction as the main shaft, propelling the car backwards.



The shift rod had a metal 'tooth' that engaged separately with three internal shift rods.  In the photo, it's sitting in N (neutral).  When moving the gearstick (in the cabin) to select 1st or 2nd gear, the tooth rotates up and engages with the upper shift rod, and slides forwards or backwards to select each gear.  When selecting 3rd or 4th gear, the tooth springs to the central N position and engages the middle shift rod, sliding forwards and backwards to select each gear.  Rotating down engages the lower shift rod, to select 5th or Reverse.

There was a metal 'safety knob' embedded in the main shift rod.  This engages with a spring loaded locking mechanism (called the 'interlock plunger') mounted on the casing that prevents shifting from 5th directly into R.



The shift rod spring provides the main force that keeps the gearstick in the 3rd-N-4th shift plane.



Forward of the intermediate flange, and in the clutch-speed casing, were the 5th and R gears.  The shift fork had swung down, out of normal position.  Ordinarily, it would engage with the 5th gear outer synchro sleeve (darker BLUE arrow), and R idler gear (LIGHT BLUE arrow).

Note that the R gears are 'straight cut'.  Whilst providing stronger engagement (greater contact area between teeth) and cheaper to construct, straight cut gears generate a high pitch whine, which is the noise you hear from a car travelling in reverse at speed.

The shift fork moves backwards to engage 5th gear.



Here, I supported the shift fork with a piece of wood.  The R idler gear spins on a short support shaft fitted in the clutch-speed casing, and is moved forwards (RED arrow) to engage R.

Note the splined end of the pinion shaft, which triggers the speedo (reluctor) sensor.

[shiny_car]

Part 3

There were remnants of blue sealant on the mating surfaces of the gearbox sections.



This was the 'speed' (gear) side of the clutch-speed casing.  The other (clutch) side was shown before (with clutch fork pivot bolt and thrust bearing support tube).  It features the:
- interlock plunger (that engages with the shift rod 'safety knob' to prevent accidental shifting into R)
- hole with bearing and oil seal for the main shaft to pass through
- bush to support the end of the pinion shaft, through to a cavity for the splined speedo sensor trigger
- short support shaft that holds the R idler gear (in position here)





I removed the interlock plunger for dismantling and cleaning.  It features a spring-loaded pawl.  The baseplate was orientated by a small roll pin; the plate was gently separated off the pin with a flat blade screwdriver.





I tried to simulate the workings of the interlock plunger to see how it prevents selecting R gear.  Whilst it blocks the movement of the main shift rod via the safety knob when moving directly from 5th to R, I have not determined the function of the spring loaded pawl, and why it was not simply a 'solid block'.  I am guessing that if an attempt was made to select R from any other gear, the idler gear, shift fork, and rods 'kick back' from the spinning gears (partly due to lack of synchro), and the safety knob springs past the pawl and becomes locked out from another attempt.  Anyone know for certain?



The intermediate flange was separated from the diff-speed casing.  1st to 5th gears are helical cut, which are comparatively silent in operation.  Two more shift forks to engage 1st-2nd and 3rd-4th gears.

Note the ends of the shift rods were bright silver.  The ends fit into the diff casing and slide in/out which keeps them polished (the rods were viewed in a previous photo, above, when diff was removed)





The external end of the main shift rod, that connects to the isostatic linkage, showed wear.  The L-shaped lever that fitted over the end must have 'rocked' back and forth; this would occur during 20+ years of forceful or 'crunched' gearshifts, causing the rod to baulk and repeatedly bounce against the linkage.  To optimise the shift quality, I have a replacement rod.



The L-shaped lever was refitted (as recommended in workshop manual) for easier grip, and the rod rotated and removed from the flange.



The internal shift rods were held firmly by spring loaded 'detent balls'.  Each rod had a ball (like a ball bearing) pressing into its side; these were secured by 'container' bolts that featured an unusual 10mm square head.  Why do engineers have to make it hard!!  Two of the bolts were easily removed, but the head of the middle bolt was recessed and difficult to access; it was also very tight, and I inadvertently damaged the head trying to remove it.

Rather than completely strip the head, I left it in place, and have ordered a suitable 10mm 4-point socket piece.  The rod was still removable, pulling out against the resistance of the detent ball.



The schematic shows the position of the container bolts (#1, called a 'plug' here) directing the detent balls (#3) against the rods.  Note the 'interlock plungers', which are small sausage-shaped rods, that also interact with the shift rods.  The tips of the interlock plungers drop in/out of detents (RED arrows) in the shift rods, functioning as a locking mechanism; a shift rod can only slide if the plunger can be pushed out from the detent into the detent on an adjacent shift rod.  If the adjacent rod's detent is not aligned, the plunger is blocked and keeps the shift rod locked against sliding.  This safety mechanism prevents more than one shift rod moving at any one time so that you can't accidentally engage more than one gear at a time.





The container bolts were hollow, for the thrust spring that pushes the detent ball.





With shift rods removed, I sat the intermediate flange and gears on my small work stand (which has an adjustable opening for the underside gears to pass).  Note the inscribed '+3' (0.03mm) on the pinion, which was a factory measurement to help calculate and set the alignment of the pinion gear (teeth), via a shim, with the diff ring gear (teeth); I will inspect the shim when I disassemble the pinion shaft.  Virtually no-one has the requisite factory tools to measure the alignment, though I won't require changing anything unless the shim shows wear.  I don't know what the inscribed 'A' or 'NLF' meant.





The workshop manual requests the 'stack height' of the gears be measured before and after disassembly to ensure everything is returned to original specification.  As long as I do the work carefully (ie: seat all the pieces properly) there should be no issue, however, as an exercise in measurement I approximated the height using a basic stand and gauge, and also 'eyed' it using a ruler!  0.03mm is the accepted tolerance (pre vs post disassembly); unfortunately, the positioning of my stand for the gauge is probably not 100% reproducible, so a difference of 0.03mm is quite likely  .



To loosen/remove nuts on each shaft, the workshop manual asked for 2nd and 4th gears to be engaged by sliding the outer synchro sleeves.  Engaging two gears at once (recall that this would be impossible if the shift rods and interlock plungers were in position) locks the shafts together, making it easier to break the nuts free.

Flipping the gearset over revealed the 36mm pinion shaft nut and 30mm main shaft nut.  It's possible to reach the former nut with a very deep socket piece (that I've ordered), but the latter requires a suitable 'crows foot' socket piece (that I've also ordered!).  There are factory tools for the job, but generic items are suitable, so my pile of new tools continues to rise!

Further disassembly will have to wait until I have the right tools.

[shiny_car]

Part 4

Meanwhile, I put more time into cleaning.  The blue sealant was evidence of the gearbox previously being opened.  I cleaned the intermediate flange of any sealant and oil (before and after shots).

I used some cheap microfibre cloths (eBay bulk buy), and plastic trim removing tool as a scraper, and wax & grease remover.







Flip and repeat:





Then onto the clutch-speed casing, gear-side:





Clutch side:





Remnants of the factory sealant (brown) were hard to remove, so mostly left.  That sealant was presumably quite runny when applied, and dried solid.



Photos of closer inspection of the gearset (final inspection will occur when disassembled).  The car has travelled approximately 135,000 kilometres, so one would expect wear on the sharp edges of the 'dog gears', outer synchro sleeves, and wear on the inner synchro rings.  2nd gear is notorious for wearing the most with subsequent grinding on gearshifts.  However, the dog gear teeth appeared quite new!  I figure it was replaced recently.

The dog gears are a separate ring of teeth, pressed onto the speed gear.  Whilst the dog gear can be removed and replaced, they are not available separately as a spare part; they come attached to a gear.  However, all dog gears (five in transaxle gearboxes) are the same, so one can either purchase any NOS (New Old Stock) complete gear, or swap a good used dog gear for a worn one.  In particular, 5th gear is used relatively less than 2nd gear, so many people swap a worn 2nd gear dog with a 5th gear one from within the same 'box, or from another gearbox.





One thing I've learnt from this project, is how the gearbox works - I'll try to explain!  Pictured, are 1st to 4th gears; 5th is similar.  All the gears on the main shaft (top of picture) are 'fixed', and rotate together.  All the gears on the pinion shaft are loose, and free to rotate separately.  Thus, when in Neutral, the pinion gear is stationary, but all the gears will be spinning (presuming the clutch is engaged).  Naturally, 1st gear on the pinion shaft spins the slowest, and 5th gear the fastest.

This short video (taken on my iPhone) shows the gears in N whilst I rotate the main shaft by hand (out of view):



Wrapped around the dog gears are inner synchro rings.  Despite fitting loosely around the dog gear, they rotate together as a single unit: inner synchro ring/dog gear/speed gear.

When changing gear, a shift rod and fork slide an outer synchro sleeve.  To select 1st gear, the sleeve on the right would slide to the right.  As it moves across, the sleeve touches the inner synchro ring.  By doing so, it 'grabs' onto the inner synchro and starts to spin together in synchrony.





To fully engage the gear, the teeth lining the outer synchro sleeve lock with the dog gear.  The sleeve slides across on a 3-pronged hub; the two rotate together, interlocked.  The hub is fixed to the pinion shaft; hence, when the outer synchro sleeve spins, it is spinning the pinion shaft and forward motion is achieved.

To select 2nd gear, the shift rod slides the sleeve across to lock into the 2nd gear dog gear.

To select 3rd gear, the 1st/2nd gear sleeve is returned to the neutral position, then the next shift rod slides the 3rd/4th gear sleeve.  Across 5 gears, there are 3 outer synchro sleeves on 3 hubs.



Video of 1st gear engaged:



The parts that a subject to wear are the dog gear teeth, the molybdenum surface of the inner synchro rings, and the teeth lining the inside of the outer synchro sleeves.

These are photos of spare parts that I may utilise to replace any worn ones.  Note the teeth lining the inside of the sleeve; then the inner synchro ring; and a spare 3rd speed gear with dog gear attached.



The teeth of the sleeve and dog gear engage and disengage during gear shifts, modelled with my spares:





There you have it - I hope that has enlightened some of you!