924Board.org

TJC · Posted: Tue Mar 16, 2021 4:07 am Post subject: Identifying LSD!!!

Hello Group, I'd like to mine the collective for some definitive information as there are many here who are much brighter than I am on all things 931.

Regarding LSD in our vehicles, are there any ways to identify, by stamping on the case for instance, whether a Porsche snailshell or Audi transaxle was equipped with LSD from the factory? I am of course familiar with the old "put it in gear spin the input shaft, (trans out of the car of course), and see if both stub axles move in the same direction, or the spin a tire method, however it dawned on me that those methods may not be absolute, especially if the vehicle/transaxle has been out of use for 30 odd years or so. It could be possible that a LSD may not "lock up" as there may not be sufficient "friction" to do so...maybe...just a thought!

In any event, before I tear into taking a side cover off for a proper inspection, I just thought that perhaps someone here could shed some light on the subject if they know of any "marks". Unfortunately I do not have access at this time to see what option codes were on the vehicles I'm dealing with, so any assistance would be greatly appreciated.

And just one more thing if I may. I believe I read somewhere here in the past that 1980 and earlier USA Turbos that were equipped with the optional sport suspension option, M471 I think off the top of my head, which included the 5 stud hubs, etc. also included a LSD snailshell trans. Any validity to this?

Thanks in advance and stay healthy!

_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11724 Location: PacNW

IMO, your frail human appendages are not strong enough to break the clutch pack free even if the LSD is completely shot.

In other words, if are are unable to counterrotate the rear tires by hand (gearbox in neutral), you likely have an LSD.

Are we talking about the 80 Getrag unit, or the later Audi one?

Also, per PET, M471 is "sport suspension" only. LSD has a separate option code.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

Snailshell will have a /12 after the usual serial number if it has a factory installed plate LSD.

Forget the input shaft. Spinning one output shaft should see the other spin in the same direction if either plate or ATB LSD. If they rotate in opposite directions its an open diff.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

TJC · Posted: Tue Mar 16, 2021 9:54 am Post subject:

Thanks Guys.
The first trans in question is the '81 Audi unit that is already out of the car and currently up for sale. I did not think that it had LSD as the usual "test" indicated that it didn't. However when cleaning it up a bit I found another number stamped into the case just under the shift linkage where it enters the transaxle. That number is 53 and I thought perhaps Porsche used that to ID whether it had LSD or not, like the /12 on the earlier units. I do remember that little tidbit from earlier discussions regarding LSD.
The reason I referenced the M471 option is that I seem to remember Dan mentioning something about the strong possibility of an '80 having LSD if it had the sport suspension as well. My '80 doesn't seem to have it, but to be honest, that car has pretty much been sitting since I found it.
Thanks again!
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11724 Location: PacNW

Found more info on some nerd site:

http://924board.org/viewtopic.php?t=22829
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

TJC · Posted: Wed Mar 17, 2021 1:09 am Post subject:

MikeDanger · Joined: 21 Nov 2002 Posts: 770 Location: Denver

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11724 Location: PacNW

Over the past 40 years, is there any chance the transaxle was changed?
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

Could have been a viscous lsd instead of a plate/clutch type lsd.. (Subaru)
I think they work more like a torque converter than a clutch..

My G31 LSD takes over 90 ft/lbs to get it to slip..
Maybe I could
Budge it just an inch or so by hand, but nowhere near able to just counter rotate the rears by hand..
Even a very worn one I would expect to put up quite some resistance..

On the other hand a viscous type is pretty easy to turn slowly, but the faster you turn it the more difficult it becomes..
_________________
80 Turbo - Slightly Modified

anthonimartini · Joined: 17 Feb 2020 Posts: 240 Location: portland oregon

oddly enough the 931 i tore apart had a factory optioned limited slip with standard 4 lug brakes. seems odd to me that someone would opt for the lsd over the huge brake upgrade. either way im happy i ended up with it as 944 brake donors are cheap and plentiful and the the g31 lsd is absolutely unobtanium.
_________________
ive saved alot of 924's
current:
79 MochaSchwartz 931
83 944
87 924S
Instagram @anthoni.jpeg
formerly known as turbellion, lost password.