Which Diff oil should I use?

Redline 75w90NS Gear oil quarts and cases (w/o friction modifier)
or
Redline 75w90 Gear oil quarts and cases (w/friction modifier)

I think I used the 75W90 (no NS designation). Honestly, I never knew there was even a second option.

^ this question was raised on another thread as well. Don't use the NS version as it is not meant for hypoid LSD's.

Just did my diff and man was that stuff nasty! Thanks for the DIY spearfish, +1

I will be doing my rear diff change soon. Can't wait to smell the stuff!!!

No problem :). Between the transmission and the diff changes, the diff was visually more pleasing to change. The amount of junk that came out was impressive. However, I didn't notice any driving difference. The tranny however had pristine looking fluid come out, but it shifts like butter now. Go figure.

Just don't get it on your hands. It's like the acid saliva from Alien. (but not corrosive, just nasty)

was there a lot of crap on the magnetic drain plug?

i like to refer to it as the devil's piss.

Oh I will make sure to have on some gloves!

It was my first time and yes there was. Make sure you clean it throughly.

Some pics from when I changed my fluid a couple weeks ago. So you guys can see the drain and fill locations.

Sorry they're so large and some are blurry. :tiphat:

http://www.liquidc4.net/images/fluids/diffplugs.jpg

Drain Plug
http://www.liquidc4.net/images/fluids/diffdrain.jpg

Fill Plug
http://www.liquidc4.net/images/fluids/difffill.jpg
http://www.liquidc4.net/images/fluids/difffillfar.jpg

Here's what mine looked like

http://i766.photobucket.com/albums/x...lDrainBolt.jpg

http://i766.photobucket.com/albums/x...nBoltclean.jpg

Just for reference, but how often should you change your differential and transmission fluid?

Don't recall of the top of my head but it is in your service manual - its the first big service IIRC...

IIRC it's something like 30k miles, but IMO if you're really hard on the car it wouldn't hurt to do it more often.