Did all Alfa 75's come with LSD?

[marks alfetta]

Does anyone know which models of the Alfa 75 came with the LSD.  Was it all of them or just those past a certain year?

[Jekyll and Hyde]

Believe it is all twinsparks and the 3.0 litre V6 - pretty sure the 2.5 V6 missed out.  V6 ratios are taller than twinspark, if you're planning to drop a whole transaxle in.

[Southern75]

not entirely correct

2.5 auto came with LSD ... i have a 2.5l with a twinspark in it (highly recommended) but you can fit the diff from and auto 2.5 into standard 2.5l transaxle.

[Scott Farquharson]

In summary, the Twinspark, 2.5 auto and 3.0 all had LSD, however the 3.0 had a 3.53 diff which makes it unsuitable for comp use.  The others typically had 4.11's.

[deano]

Hey guys,

I dont understand the whole LSD thing properly and was wondering if someone could explain it to me. I've just got my Ps and have been racing go karts for the past 2 years so i havnt really needed to worry about diffs.

I know how an open diff works and I understand the purpose of the LSD and why you need one over an open diff, basically to get power down out of corners or you'll end up spinning the inside wheel at 100% and going nowhere fast (as well as revving the pants off your poor old volvo 360 )   

Doesnt an LSD lock the wheels together in a certain % ratio using clutches? So for instance the LSD in a 3.0 potenziata is 25% (so im told) so if one wheel is spinning at 100 km/h the other is spinning @ 25km/h?
Am I sort of on the right track Can someone explain the percentage thing??? Why do people put 50% LSDs in for comp use???

So the twinnie and 2.5 had 4.11's and the 3.0L has 3.53, didnt the 3.0L qv potenziata have different again, like 3.73, or 3.93 or something??

Why is the 3.0L unsuitable for comp use? Is it because you cant go as fast in each gear compared to the TS and 2.5? from what i can remember, the TS does 80 km/h in first i think, havnt driven one for a while! So wouldnt the 3.0L ratio be suitable for slower twisty tracks?

Over the next year, I want to slowly build a 3.0L potenziata track car and many people have said go the TS. Is it the diff thing or is there more to it?

cheers

Dean

[Rob Berson]

Can one tell if a transaxle has a LSD by jacking the car up out of gear and turning one wheel - if the other turns in the same direction then it has a LSD diff? If the opposite wheel does not turn in the same direction does it definitely mean that it is an open diff?

Rob

[Mat Francis]

Rob: if the opposite wheel turns in the OPPOSITE direction, it is indeed an open diff.

[scott.venables]

From what I've read, it's not that easy to tell.  Because of the way Alfa LSD's are, the require load before they start to limit slip.  This is of course different to locked diffs where both wheels turn 1:1 in the same direction all the time.  The 25% quoted is where 25% of available torque is transferred to the slipping wheel.  Have a look at: http://www.alfabb.com/bb/forums/milano-75-1987-1989/51915-how-identify-lsd-limited-slip-differential-2.html for another discussion on this and a bit of to-ing and fro-ing.

I think people are probably saying don't turn a Potenziata into a track car, well, because it's a Potenziata! They are reasonably rare. The diff thing might come into it as well because the taller diff ratio in the 3.0 isn't as good for acceleration as the 4.1:1 in the 2.5/TS. 

Cheers, Scott

[deano]

hey guys,

wondering if anyone can help me identify my spare transaxle. At first i thought it wasnt an lsd cause if i turned one wheel, the other went in the opposite direction. It turns out it is. 

the potenziata had a 3.5 or 3.7 diff ratio i believe. I think the spare is a 4.1:1 diff out of a normal 3.0L.

the crown wheel has 41 teeth and has 11 41 bib on the side. that has to be a 4.1 doesnt it???

the id is: 4061 004243 903091 S25

Does anyone know what gear and diff ratios i would need for a 3.0l track transaxle?

cheers.

deano

[Jekyll and Hyde]

the crown wheel has 41 teeth and has 11 41 bib on the side. that has to be a 4.1 doesnt it???

41 divided by 11 = 3.73

[BradGTV]

hi just a question to add

is it possible to put the diff of a 75 onto my GTV 2.0 gerabox??
cheers, brad

[alfagtv152]

Hi All,
For me I think the only way to know what the diff centre is is to sight it,the only test that gets anywhere near it is Paul's suggestion to see if you can spin both wheels on a loose surface.
As far as changing centres from trans to trans is yes it can be done but various bits of machining need to be done to position the diff centre correctly to mesh with the pinion after you have fitted the desired crown wheel to match the pinion in the gearbox.Even 105 centres can be fitted to Alfetta transaxles with the correct mods.I will attatch some pics of a limited slip centre,an open diff is easily recognised by seeing the very open area with the sun gears very obvious.
Cheers
Andrew

[aggie57]

Fitting an 105 LSD to an Alfetta transaxle is pretty straight forward although you'll need later V6 style stub axles as the shaft is bigger than on early Alfetta's.  That's the shafts that slide into the splines shown in Andrew's photo's either side of the diff centre.  It passes through the casing and bolts up to the brakes/half shaft.  They were always in pretty short supply and someone else will know if later GTV's , 75's etc came with the larger shafts.

The other major thing I remember needing was a spacer that fits to one side of the LSD centre as it's narrower than the standard open centre.  Can't recall where exactly it goes but Vin Sharp knows.....!

[Storm_X]

Does anyone have a picture of a 75 center ? Ive never seen one before.


There is so many sides of this topic to know how you diff is LSD or not, but my 83 Giulietta is open wheel and it spins 2 wheels on grass. When it comes to tarmac it does spin both wheels with 13 or 14" wheels but with the wide X wheels it spins two wheels sometimes and single also but because of it spinning the one wheel i cannot call it a LSD.