Honda shifter conversion...

[bazzbazz]

Marvellous Mechanical Manipulation 

[johnl]

Thanks Baz,
Notice how close the gear knob now is to the steering wheel, in any gear. This in itself is nice, no more reaching for a fairly distant gear lever, the shifting hand now almost just drops straight onto it, no matter what gear has been selected or is about to be selected. Once the shift is made, the hand is already almost back on the wheel. When shifting, no gear is more than a 'snick' away from any other gear.

There is still about 1cm of both lateral and longitudinal 'free play' at the gear knob, which seems to be caused by internal clearances in the selector mechanism inside the gearbox itself, probably not much I can do about it. Still, lever sloppiness is much better now that clearances and deflections in the shifter itself have been minimised.

There is still a hint of 'drag' in the shift action, which I'm pretty sure is mostly to do with the cables rubbing against their outer sheaths. Cleaning them out and using a lighter lubricant might help, but disassembling the cables seems very difficult (had a look while they were off the car, couldn't see an easy way). A rod mechanism would be a bit better than cables, but a nightmare to create because of things in the way, the need for cranks and a multiplicity of added pivots / joints (would probably end being ridiculously complicated). 

I used a general purpose grease to lube the guts of the shifter, which I suspect might be a bit too thick and may be adding to the hint of drag. A lighter grease might be a better bet, or a thickish oil. At some point I can see it coming off for a change in lubricant.

Overall I am very happy with this and it's a huge improvement on the stock set up. I shouldn't get too hung up on trying to make it absolutely perfect, that's a high bar...

Regards,
John.

[johnl]

Today I tried driving the car with the longitudinal gear lever throw set at it's shortest possible setting (as made possible by the multiple cable attachment points on my modified gearbox linkage). The result is that the longitudinal throw became super short, and uber 'snicky', but very unpleasant to use. Lever movement became way too stiff and 'sticky' in operation, a pity because I really liked the incredibly direct nature of the action.

I suspect this problem is caused not so much by the reduction in overall leverage in the mechanism, but that attaching the cable at the shortest possible effective lever length (gearbox end of cable) means that the angle of the cable becomes too acute where the cable sheath attaches to the gearbox and the inner cable passes out of it. So, as the cable moves through its' sheath at the point where the sheath attaches to the gearbox (actually on a casting bolted to the gearbox), the cable itself is forced to move through too tight a bend. This seems to cause friction / 'stiction' in the cable because it is rubbing too tightly against the side of the gearbox end of the cable sheath.

This could probably be freed up by modifying the casting to which the cable sheath attaches, to alter the angle at which the sheath attaches to the casting, but life is too short and I can't see myself trying to do this. The shift action is smooth and light at the next closest adjustment, and provides a much shorter than stock lever throw, but it's just not as 'super snicky' as at the shortest throw setting (good enough...).

In the meantime I've discovered that there is significant play in the two plastic bushes at the gearbox lever arm arm (the one associated with the lateral shift throw). These bushes seemed fine when the parts were on the bench and when the linkage is manipulated by hand from inside the engine bay, but when an assistant wiggles the gear lever from inside the car there is obvious play due to wear. Ordered some new ones today (Ebay from the UK - AUD$8.33 plus AUD$5.05 post).

Regards,
John.

[bonno]

Hi John
Firstly I must say your gearbox lever mod is quite impressive to say the least and quite intricate in detail for adjustment. I think you will find that the replacement of worn bushings might rectify the stiff and sticky operation of lever movement (fingers crossed).
Regards
bonno

[johnl]

Hi Bonno,
I don't think the wear in the plastic bushes creates any stiffness or other issues with the shift quality, other than to cause a bit of slack / free-play in the lateral plane (as seen at the gear stick). It's not a big deal, it just affects the 'niceness' of the shift action.

On the other hand the stiffness etc at the 'short' adjustment setting was interfering quite badly with the shift action. It was occurring only at a particular adjustment, and seems to be associated with what happens to the cable at this adjustment position (nothing to do with the bushes, that I can see).

I'm not even sure whether (or not) replacing the bushes will improve the lever free-play that is there now. A degree of lateral lever slackness may quite possibly exist even with new bushes. I suppose I'll find out.

I suspect that plastic isn't the best choice of material for such bushes, not exactly 'precision engineering'. Bronze would be better (or, if $ were really no barrier then needle roller bearings...).

Regards,
John.

[johnl]

A few days ago I fitted some new bushes in the crank lever (at the gearbox end of the mechanism, associated with the lateral gear stick throw). I was a bit surprised when the new bushes fitted the pivot shaft (OD) quite a bit more loosely than the old bushes did. On the other hand, the new bushes are a much tighter fit into the ID of the holes in the crank housing, so inserting them was quite a bit more difficult than it was with the old bushes (which would just slide in and out with almost no resistance).

It seems that insertion into a 'too tight' hole squeezes the bushes enough that they become a closer fit on the pivot shaft, taking up all or most of the clearance between bush ID and shaft OD. There has been just a very slight increase in 'stiction' associated with lateral gear lever throw, which I assume means that one or both of the bushes is / are now just a tad too tight on the pivot shaft (and this very slight tightness may disappear with more use?). This is not enough to be irritating, just noticeable if you are trying to notice it. The shift action has been tightened up somewhat, in that there is now noticably less 'free' motion at the gear lever than there was previously.

Oddly, this shows up not only in the lateral gear lever throw, but also in the longitudinal throw, both of which now have somewhat less 'lost motion' (i.e. gear stick movement that doesn't actually do anything inside the gearbox). I'm at a bit of a loss to understand why this is the case, since these bushes are involved only with the part of the shifter mechanism connected to the cable that is responsible for the lateral lever throw, not the longitudinal throw. A bit weird...

There is still something in the linkage that isn't quite right. I suspect the stock plastic joint at the shifter end of the longitudinal throw cable might not be quite 100%. Sometimes there is a subtle 'click' that ocurs simultaneously with slight 'snatch' in the gear lever motion when pushing on the gear lever, say shifting out of second or fourth gear. Even though the joint seemed perfectly fine on the bench, I suspect the load involved in actual use is causing some slight internal movement. In retrospect maybe I should have tried harder to fit a spherical rod end at both ends of each cable, rather than just at the gearbox end.

At any rate, in the end all this has been well worth it. The shift action is now very good as opposed to fairly crappy. I can't say that it is definitely better than it would have been had I fitted a brand new stock shifter, but I'd be very surprised if it isn't. I'm also confident that the Honda shifter will last more or less indefinitely without significant wear, especially since the shifter had already done nearly 300,000km in the Honda and still seems pretty much wear free, whereas the Alfa shifter is known to wear significantly.

Regards,
John.

[johnl]

Changed the gearbox oil yesterday, just because I had no idea of when (or if ever) it had last been done. There is no mention in the service record, could easily have been the original fill (especially as AR doesn't have a gearbox oil change anywhere in the service schedule).

The old oil appeared yellow and clear in the stream as it drained out, and a little 'cloudy' in the drain tray. It may (or may not) have been replaced by the previous owner, or at least not all that many years ago (?). Reassuringly, there was very little evidence of metallic particles in the old oil or in the tray (I've seen much worse in oil from gearboxes that were still operating perfectly well).

I have no idea what brand etc the old oil was (or its age, as above). The new oil is Penrite Pro Gear 75w/85 ("full synthetic"). It was worth changing oil because the shift action now feels noticeably smoother / slicker than previously, with a little less force being needed to select gears, and less 'baulky' (not that this was bad before, but occasionally...). When I place my hand on the gear stick there seems to be a bit less vibration in the stick than before, but possibly placebo. Possibly also all in my head, the drivetrain / car feels just a touch smoother in general.

All this may simply be due to new oil replacing old oil, or it could be that the Penrite might be a better oil than the oil it replaced, or perhaps a combination of both. Whatever, I'm very happy with this oil in this gearbox. It does say "smoother shift" on the bottle, but maybe I'm more suggestible than I'd like to think...

I was a little worried about changing the oil to something that was a bit of an unknown quantity because I once used a 'fully synthetic' gearbox oil in my old Accord (one of the Motul products, the one that is suppsed to work well with synchomesh). This oil was very good (and very expensive...), with much nicer shifts and shift feel, except that it became very difficult to select first gear at rest, to the point that I had to get rid of it (problem disappeared with Honda branded MTF).

Regards,
John.

[johnl]

Followers of this little journey may recall that I still had a slight problem with the shift action. I said:

"There is still something in the linkage that isn't quite right. I suspect the stock plastic joint at the shifter end of the longitudinal throw cable might not be quite 100%. Sometimes there is a subtle 'click' that ocurs simultaneously with slight 'snatch' in the gear lever motion when pushing on the gear lever, say shifting out of second or fourth gear..."

Well, my suspicion was incorrect. It was nothing to do with the cable joint, but to do with one of the cables (itself). Turns out that one of them was actually broken. At the greabox end of the longitudinal throw cable, the outer sheath had fractured where it fits inside the metal ferrule (i.e. the machined fitting that holds the end of the cable sheath and is attached to the cast aluminium bracket that is bolted to the gearbox).

When the gear lever is pushed or pulled (longitudinally) it pulls or pushes on the inner cable 'wire' (to state the obvious). When a cable's  inner cable is placed in tension it creates a compressive force in the cable sheath. When the inner cable is placed in compression then the sheath is placed in tension. If the cable sheath is broken (in this case detached from its' fitting), then the sheath will move as the cable inside it moves, pulling away from the ferrule as the inner cable is pushed, and then moving back against the ferrule when the inner cable is pulled. Not surprisingly this causes a degree of sloppiness in the linkage action.

My broken longitudinal throw cable sheath was moving by several millimetres as the inner cable was pushed / pulled. This was creating unwanted lever motion as well as the "subtle click and snatch" that I could feel in the action. Note that I am using the past tense here, because It's been fixed.

I made a semi tubular bracket that attaches to the outside of the cable ferrule at one end, held in place with a hose clamp. The bracket extends along the cable by several cm and becomes smaller in diameter so that it can be clamped to the outside of the cable sheath, again with a hose clamp (smaller one, of course). Forces acting between the ferrule and the cable sheath are now reacted within this new bracket, rather than in the failed connection between them.

This has worked extremely well. The "click and snatch" is now completely gone, and lever motion is less and smoother then before. Care needs to be taken when tightening the clamp onto the bracket where it wraps around the cable sheath, it's possible to crush the sheath against the inner cable and seize it up. It would most likely be better to use two clamps tightened less tightly than one clamp more tightly, as this would create less risk of crushing the sheath tube while still providing adequate grip between the OD of the sheath and the ID of the bracket (to prevent one sliding on the other)

Of course a better solution would be to replace the defective cable, but new ones appear to be very expensive (at least on a well known auction site, around $280.00 inc post from UK), and I suspect even second hand probably not all that cheap. Also, removing / replacing a cable is not to be taken lightly since access is very bad. This repair has cost more or less $0.00.

After all this effort and as the shifter now feels to use (fantastico, really!) with all gremlins sorted, I would not be all that surprised if this particular 147 now has the best shift action of any other, anywhere (if so, then probably 156 etc too...). This might be with the exception, maybe, of cars fitted with one of those racing style shifters, but then I would imagine nearly all of those would be track cars because the race shifters I've seen are not very road car friendly (take up so much room...).

Regards,
John.