Author Topic: Diff. Fluid does it matter? (Read 2806 times)

Murdul · « **on:** February 10, 2009, 09:56:06 PM »

My question is this if i put LSD formulated fluid in my differential and I do not have an LSD is this problematic? I know the opposite has ill effects.

I recently acquired a 91 318iS in Washington state. I love it. I do not know whether or not I have an LSD. I have looked all over the rear diff. and there does not seem to be an identification plate. There are some numbers cast in
19 1 2 9 90 on the drivers side, a small box with unreadable characters between the 9 and 90 also
666 40 on the passenger side
I do not think these mean anything but just in case I am wrong let me know.

szed03 · « **Reply #1 on:** February 11, 2009, 12:16:37 AM »

Jack the rear end up with both wheels off the ground, trans in neutral. Spin one wheel forward...if the other spins in reverse you have yourself an open differential. If both wheels spin forward you have yourself a limited slip diff.

As for fluid, just put in a good 75w90 (Mobile 1, Royal Purple, Redline, Amsoil, ect...). No need to put spend money on LSD additive unless you need it right?

Hope that helps.

Murdul · « **Reply #2 on:** February 11, 2009, 04:02:57 PM »

Thank you for your reply. But the question still stands. I am assuming fluid formulated for an LSD will not negatively affect a non-LSD differential. I will jack my car up and check soon enough, I just wanted to buy the fluid now so I don't have to run back and forth. Everything is far away from where I live and if I can pick something up on the way home from work that makes it easier.

szed03 · « **Reply #3 on:** February 12, 2009, 04:47:35 PM »

Limited slip additive in gear oils won't affect anything in an open diff.

CCR Engineering · « **Reply #4 on:** February 18, 2009, 06:22:08 PM »

The additives are simply friction modifiers for the plates in the clutch, if you have no plates you have no problem.