rockatansky

Hi, obviously reading the option codes. But when I bought the car it doesn't have any card talking about the optional codes, and also it doesn't have the decal at the rear trunk with the codes.

So my question is if there is some way to know if it has the 'Limited Slip Differential' (option code 220 I think) or not.

It's a 1980 928, vin: 92A080nnnn. Right now the car is beeing repaired and I can get near the trans from under the car If your advice is to looking for something there. Thanks.

ps.- (probably I will end up asking Porsche for an authentification certificate (100$), but in the meantime I would like to know if it has LSD).

tmpusfugit

The most reliable method is to put the car in gear, or park if auto, with the back end jacked up and wheels off the ground. Turn one wheel and if the other wheel rotates backward, NO LSD. If they both rotate the same way, you have LSD. And thanks to Landseer for that quick method of determining LSD. I was looking for a part number and never considered the easy method until he suggested it...

rockatansky

thanks tmpusfugit, nice way to test it. I would see how can I check it. The problem is that the gear lever is right now taken apart (I think with the trans in neutral) and I can not engage a gear right now...

neilh

PM me the full VIN and i'll look it up for you in PET - that wil tell you if it was delivered with LSD

neilh

Replied to PM, does not have option 220, sorry.

Landseer

^^ good initial indication, but not always accurate due to hardware replacement over time.

Stampings under transmission are another.
In picture below, it is an 83 box, no LSD.
Should have been 84 box, with LSD by vin
(codes vary by year / deciphering is within tech docs)
Somebody swapped the box.

LSD units are modular and can be swapped in and out.


Spin test is one way. Even if clutches are thin, I think it will work. Search, others have done this for automatics and manuals, plus have a torque wrench test method to determine clutch condition of LSD.

Removing the back cover is best way to confirm. Have another gasket ready though.
In picture below, the LSD trans is on the right.

Plenty more information on ID of units available with searching this forum.

Gregg K

With the car in gear, or park, both wheels will not rotate forward. Not unless you break the pinion gear off.

I don't think this is really an honest way to check, but with the car in neutral, one wheel on the ground and one off the ground, rotate the wheel, and the clutch pack may engage. But I've read that even that isn't always going to give an indication. It works on my car, and on my other vehicle. If it does, then there should be some effort involved to turn through the friction of the clutch pack. Something along the lines of 20 lb-ft or more.

rockatansky

With the help of Neil, I know that my car left the factory without LSD. The only doubt now is if it was installed later (I suppose not, but not sure).

Landseer, seeing the code of your first picture (11D 5597), what should say if it has LSD?. (I think I prefer not to open the transmission to see if it has lsd). Thanks.

Landseer

Neils same vin trace method caused us to find an LSD in a car we didn't realize had one (we had never checked the trans number)!

If working only from trans numbers, like above:

There would have been an additional "12" before those numbers.

Below is the stamping from a different transmission entirely.
Its from an 85 USA. A28 automatic. See how the 12 was interjected to denote LSD?
Indeed, it has one. Makes a world of difference on my gravel driveway hill.

The decode sheets are shown below also.

rockatansky

Neil was giving me this information through pm. This forum is great!. As soon as I can get down there I will check the codes to see if some previous owner has changed the trans to an lsd during this three decades. Thanks a lot!.

tmpusfugit

You are of course correct....I ran my mouth without thinking it through, nothing new about that. This test would be "leave the car in neutral, be it stick or auto, rear wheels off the ground they should both rotate the same direction, and if one wheel is is "stopped" the other would also "stop" to the limit of the torque supported by the LSD clutches. If I correctly understand how the clutches work on the LSD they are always "engaged" on the 928 up to their holding limit, unlike some "lockers". If one wheel spins while the other is on the ground or stopped by other means then you most likely do not have an LSD. But, as others have stated perhaps the only real way to be completely certain is pull the cover and look......

Erik N

Rockastanski

My '78 has LSD. Trany stamp says: G28/03/12 1118 2763

Re your avatar, I agree that the first 10 minutes of the original Mad Max are the best 10 minutes of cinemadom, ever.

rockatansky

Thanks Erik. Mine is 5 speed too and should start with G28, I will search for this '12' in the third position to know if mine has lsd. I'm not home and can not take a look. The car is on jack stands so no problem getting there.

Right now I'm waiting for a shipment from 928motorsports of a 'precission ball cup' and a 'short shifter'. Are they the same you have on your car specs?.

(I'm glad you identified my avatar, I agree with you about the first minutes in madmax.)

Dave928S

Chris posted those photos of LSD and the standard diff centre and you can see the spools are visibly very different (spider gears visible on the standard centre).

You can still do a visual check, without removing the rear cover, by using an endoscope/fibrescope (if you know anyone who has one), by removing the fill plug and looking into the case from there.

Erik N

I have a DEVEK short shifter, not sure how it differs from 928M's.

The precision ball cup is a great upgrade. It gave my car a much more notchy feel to the shifter- you cat really feel the gears engage. Excellent.

Installing it is a HUGE PITA! as there are 3 or 4 separate threaded bits to it, everytime you turn one to adjust or tighten, the others move a different way. I installed mine while the engine was out. I ended up holding everything in position with a wrench from inside the bay, while a buddy applied rotation to tighten it by moving the shifter sideways inside the car.

I can't imagine installing it w/ an engine in the way... but where's there's a will there's a way! After it is done and adjusted, put a couple of blobs of JB weld putty on the outside to ensure it doesn't EVER come loose.

It will be worth it. Good luck!

And here is the first 10 minutes of Rockatanski's fame:

http://www.youtube.com/watch?v=7GKP_dB3Hmw