Author Topic: Gbox and Diff Oil (Read 3267 times)

finite · « **on:** May 17, 2009, 12:42:17 PM »

Afternoon all!

I'm about to undertake replacing the drivetrain fluids... problem is I have no idea what fluids to use. Having taken a look underneath there are no lables (green or orange) with the fluid types on. I have a UK spec 1991 E30 318IS with an open rear diff.

Open to suggestions with supporting arguments!

Car is my track day thrash machine so gets some real abuse. Here's what I've found so far:

Diff Oil:
75w90

Gearbox oil:
BMW Green label (SHC 630) Max-Gear 75W90

BMW Red label (DEXRON III) Synchromax

BMW no label (80W GL-4) SAE 30

DesktopDave · « **Reply #1 on:** May 17, 2009, 09:15:07 PM »

I used Valvoline synthetic 75w90 gear oil. I had no tags on either 'box or diff. I'm told you could also use a high-quality SAE 30 oil in the owner's manual.

I've heard really good things about Red Line gear oils, your open diff won't mind friction modifiers either. Since it's a track car you might want to swap out the diff rear cover for the Motorsport unit; it's finned with extra capacity and doesn't overheat & ooze oil like the stocker does.

So far both 'box and diff are quiet and shifting well. On other cars I've owned, the swap to synthetics may have increased my gas mileage slightly. It made cold-start shifts FAR easier, especially in below freezing weather.

nicknikolovski · « **Reply #2 on:** May 18, 2009, 05:57:06 AM »

I used Castrol's Dexron III product for my manual transmission (Red label) and Castrol SAF-XO (Fully Synthetic 75W/90 Non-LSD gear oil)

JP 91iS · « **Reply #3 on:** May 18, 2009, 01:30:20 PM »

I used Redline MTL in my red-label transmission and Redline 75w90 in my LSD. I was told the MTL is good for our manuals, even though they are specified to use ATF. So far all is great.