I see the advice to look for an 87-89 325i with an LSD but how do you tell it has one? The eight bolt diff? Do I understand there is a tag or a marking of some sort on it?
How to identify an LSD car
kchildre
#2
A limited slip came standard on the "is" cars, but that’s not to say it hasn’t been removed or replaced at some point in time. There is (or should be) a tag on the differential. The tag should begin with S 3.73 …
Here is a picture of mine, it’s the M differential cover (which I added) but the tag is from the original "is" differential
take a brass toothbrush with you. look for the S before the ratio. Also, if it is out of the car, there should be an S painted on the top of the diff
Igor
#4
Or if the tag is missing, put the rear of the car on the jack-stands so that rear wheels are off the ground. Spin one tire by hand and observe rotation of the other tire – if they spin in the same direction diff has LSD, if not it’s open diff. To approximate diff ratio, count and compare number of times tire and drive-shaft turn.
HTH,
Igor
edavidson
#5
Igor - FYI, this is one of the tech checks at Nationals - marking drive shaft and checking rear diff ratio by rotating wheels while on jack stands.
Ed
victorhall
#6
You guys are way too scientific about this!!
Step 1: Start car
Step 2: Press in Clutch and hold
Step 3: Apply Throttle liberally
Step 4: Release Clutch
Step 5: Count the number of black marks behind the car. 2 marks = LSD
Step 6: Reassure neighbors that you’re performing experiment in the name of science.
Step 7: Send large check to Victor Hall.
scottmc
#7
Very helpful info… I always thought the LSD cars were the ones with the rainbows trailing behind it :pinch:
ilateapex
#8
Sometimes the both wheels off the ground will not tell the tell. You only need to jack up one side. If you can spin the wheel it is an open diff. if you cannot spin the wheel it is a LSD. You can put a wrench on one of the lug nuts to try to spin it. A LSD diff should not spin or at least be very hard. This is also how you check the % lockup as outlined in a previous trend.
Michael O.
GTS1/KP/ITS
