Tranny Fluid VS Gear Fluid?

[mace]

I just bought a 95 M3 5-spd and I'm in the process of changing all the fluids in the car. When browsing through this forum, I noticed people mentioned D4-ATF (tranny fluid?) & 75W90NS (gear oil)? In addition, I also noticed people put 75W90NS in their tranny? Which way is correct? I'm new to RWD cars, so this thing is new to me. Does RWD cars have a specific oil for differentials & trannys? Please help, thanks!

[sfmng]

Redline D4 ATF goes in the tranny. Some folks use Redline MTL, Mobil 1 ATF, Amsoil ATF. Most, including me, use the Redline D4 ATF in the tranny.

75W90NS goes in the diff. I'm running Redline in the diff also.

Before changing the oil in tranny/diff, make sure you loosen the fill plug before you drain it. Don't want to drain it and find out you can't get the fill plug off!!!

Have fun.

[sfmng]

Oh...you'll need a pump too to get the oil into the tranny/diff. Do a search on this forum on oil changes, etc. and there are some very well documented instructions to get you through the process.

I use to do most maintenance myself, but now, I just let my mechanic wrench everything on my car since he already has all the tools/knowledge to make it easier...(especially the hydraulic lift). I just like driving the car. :buttrock

[fourfa]

75W90NS is for people with no limited slip, i.e. not the M3. use the redline 75W90 (not NS) or the equivalent Mobil1, Lubromoly, Motul, etc.

[UD///M]

What fourfa mentioned is very important. NS cannot be installed in a limited slip differential. It could probably go into the transmission since it does not have the friction modifiers. A limited slip diff requires different oil.

Aside from that tranny oil and gear oil are the same. ATF is being used more frequently by manufacturers for manual trannys because it is thinner and provides for better cold weather shifting. It also allows for less driveline loss.

[mace]

Thanks fourfa and UD///M for the heads up. I have purchased the 75W90NS, but it's a good thing I have not put it in yet. I will go and exchange it for the 75W90.

[sfmng]

Sorry Mace for not catching the "NS" on the diff oil. I just copied what was on the initial post without thinking. :(

Thanks to UD///M and fourfa for catching it. It would not have been fun filling a limited slip diff without the required friction modifiers in the oil.

[michaelab]

Originally posted by sfmng
It would not have been fun filling a limited slip diff without the required friction modifiers in the oil.

Happened to me - I didn't do it, the BMW dealer did!! It's not serious but what happens is when you make a sharp turn slowly you get a horrible periodic grinding/scraping sound coming from the diff. When I noticed that I checked the service printout and noticed they'd used the wrong oil. Went back and they changed it - a few figure of eight loops later (to allow the new oil to work itself into the clutch packs) it was all fine - phew!

Michael.