Option code for LSD in a 915?
 

Anyone know the option code for LSD. I believe my SC came with it but I suspect it needs replacement or adjustment. I have no experience with this type of setup. I'll be pulling the trans to look into the 5th gear issue discussed earlier this week. While I am in there I would like to check the LSD out.
Thanks,

all i know is there is a 12 stamped among the numbers on the rib under the diff if it has posi from the factory.

The option code on my 84 Carerra w/LSD is "220". I think the code should be the same for your SC. BTW; it also has the "12" stamped on the bottom of the trans case as mentioned above.

Hope this helps:)

Goth,
Do you happen to have a picture of this "12" where it is stamped on the transmission. I'm pretty sure that I'm not one of the lucky ones, but I'd like to make sure. My car has surprised me in the past. I do not fell like placing it on jack stands just to try the rotation test.
Thank you,
Matt

On the bottom raised surface....looking up...placed between transmission type number and serial number you should be able to see "12"....

http://forums.pelicanparts.com/showthread.php?s=&threadid=94585&highlight=Ferch+l imited+slip

- Wil

Hayden posted these a while ago
No lsd
http://forums.pelicanparts.com/uploa...1160660584.jpg

w/ lsd
http://forums.pelicanparts.com/uploa...1160660639.jpg

Very nice, thanks guys!

OK guys,

What is the difference between M220 and M221 (BA p. 256)?
M220 – “Locking differential”
M221 – “Porsche-locking differential”
(There is the same distention in the Kindel list.)

I have seen LSD transmissions with an “11” in place of the “12”. What is this?

Best,
Grady

the first character is the type - G is a Getrag

the next 4 are the version -G5001 is an early Getrag 5 spd g50/01

1 as the next digit means open diff, 2 is M220 option lsd G50012 is a 40% lsd diff.

the next digit is the year

the last 5 digits are the serial #

can't find any info about M221 except it's in there starting w/ the '87 Getrags

Mine is stamped:
915/62 731 4913 No "12".

Stupid question: If I don't have LSD, why would have I been able to leave two strips of rubber between first and second? Before flaming me for speed shifting, this was before I blew out 2nd doing this. I don;t drive like this anymore.

sometimes you just get lucky

But I'm married.



Oh, c'mon, you were thinking it.:)


Thanks for the info, Bill. One less thing I have to worry about inside the tranny.

You might have gotten lucky and had a PO put in an LSD with a prior rebuild. Here's a simple test that will tell you for sure what you have, regardless of option codes or transmission stampings:

Jack the rear of the car up so both wheels are off the ground. Ebrake off, car in neutral. With your hand, spin one of the rear wheels. If the other wheel spins the same direction, you have an LSD. If they spin opposite directions, you have an open dif.

With any luck, maybe you'll find something from GT in there.

I've got a 915 with the stamp: 915/62 AT 731 3506

The output flanges spin in opposite direction. I'm assuming it's sans LSD, but does the 731 mean the 7:31 R&P? And what does the "AT" mean? I've never seen the "AT."

there were 2 systems used thru '81 and '82 up

for yours this is the trans id
731 3506
7- type
3- version
1-model year 1981
3506- serial #

if there was a lsd it would rear 915/61 12 731 3506

I have no idea what AT means

Thanks, Bill. Another trusted source has never seen the AT either.

Maybe you left two black stripes because you were pointed straight ahead ??

...might be a different story trying to put power down in a high-g, tight radius turn....

- Wil

Yep, that would be my guess. With an open dif, the power wants to take the path of least resistance. With the car level, pretty much equal weight on the rear tires and the same tires on each side, it's not impossible to spin both wheels at the same time. Both tires present the same load to the diferential, so they should, in theory, spin at just about the same time.

Now, if there is an imbalance, then one wheel will spin while the other doesn't. Like, one tire loaded in a turn and the other unloaded. Or one tire stuck in the mud and the other on the ground, a la My Cousin Vinnie.

I'm having a hard time believing that an open diff. will allow both tires to lay down rubber at the same time. Even on a perfectly level surface there will be an imbalance in the torque and grip at each wheel. When that imbalance occurs (likely at the initial application of power), the power will be tranfer to the slipping wheel (or wheel with less traction) and stay there.

I can't believe all the responses, with all this going round-n-round.....

....just jack the rear up and hand spin one of the tires...see what happens on the other side. If it spins in an opposite direction...there's no LSD or the clutch pack has worn even if it WAS delivered as LSD. If it spins in the same direction, you have LSD and a functional one at that.....


- Wil

Wil,

Can you explain how an open diff. would leave two rubber strips in a straight line? I'm not trying to beat a dead horse or keep the merry go round going around, but the post about leaving two rubber strips with an open diff has peaked my curiousity.

Souk:
No question that an open diff will bias the torque to one side...however, it's been mentioned a number of times here (as well as by magazine testers), that the extreme rear weight bias of a 911 will tend to mask the open/closed ( or shall we say.."semi-closed" ) differences in the differential.... that are more readily seen in front-engined, rear-drive, but front-weight biased cars.

So...yeah, as much as you'd expect one long stripe regardless of where the car's masses are located, the extreme rear heaviness might have you see two stripes even with an open diff. Or at least the *tendency* for that to happen might be more probable on a 911 than for any other car.

As I said....why quibble?...why not check tire rotation to see if the LSD effect is there..that was the original qustion anyway, right?

- Wil

Alright, the original poster could just jack up the car and test for LSD, but this is the first time I've heard an non-LSD car leaving two strips. I've got an E30 BMW with an open diff. and it will leave a single strip all day long. My '76 911 sans LSD will do the same thing. I've never seen it leave two strips, but I sense wheel spin (one wheel) on wet or dry surface in a straight line or corner. I'm not trying to be contrary, I just have never heard of this or read about it in the 20+ years that I've been a car geek. I guess I'm just non-LSD ignorant. ;)

Me again.
I have used the rotate one wheel and see what the other does method. They rotate in the opposite direction. For whatever reason, the car woulpd leave dual marks on the pavement on the 1-2 shift. I don;t speed shift anymoe so I don't know if it will do it now. I know that she came from the factory without LSD.

what about if you spin one wheel and the other doesnt spin at all?

In that case, I would leave on the jack stands for a while....

I know someone said put it in neutral, but I think you need to put it in gear for the wheels to spin in opposite directions on an open Diff.

You may think so, but in reality, most cars will not peg-leg in a perfectly straight line.

AT stands for Austausch, replacement....A bit late for the reply.

Cees