How can I tell if its an LSD?

[ANDRÜ]

Heres the story. I have a 1987 325 right now, an eta, and really want a different diff, something geared lower. Not long ago I got a parts car, a 1990 325i auto. I did some ressearch and found that this has a 4.10 differential. How can I tell if it has an LSD or not? I cant do any burouts since the car doesnt run, so is there a tag or serial number that distinguishes an open vs. LSD?

Thanks

[erik325i]

Yes, there is a tag bolted onto the diff cover that will say what gear ratio it is and whether or not it is an LSD.

If it is a LSD, it should say S410xxxx meening it's an LSD of 4.10 gear ratio.
An open diff would just say 410xxxx.

Also, if you jack up one of the rear wheels and leave the other on the ground, you should not be able to spin that wheel if it is an LSD. With an open diff you would be able to spin the lifted wheel.

-Erik

[Mike325]

Yes, there is a tag bolted onto the diff cover that will say what gear ratio it is and whether or not it is an LSD.

If it is a LSD, it should say S410xxxx meening it's an LSD of 4.10 gear ratio.
An open diff would just say 410xxxx.

Also, if you jack up one of the rear wheels and leave the other on the ground, you should not be able to spin that wheel if it is an LSD. With an open diff you would be able to spin the lifted wheel.

-Erik

That is how you check.

This might be helpful too.

http://www.r3vlimited.com/board/showthread.php?t=66460

[ANDRÜ]

Thanks guys

[Tangent]

Also if both wheels are off the ground: Make sure the e-brake is off and trans out of gear. Turn one of the wheels. If the wheel on the other side spins in the same direction, it's an LSD, if it spins in the opposite direction it's an open diff.