Rear Diff Fluid
 

Whats the best stuff to use when doing a change? Should i go with something synthetic? How often should it be done in my 87 300SDL, and how much should i buy to prep or this job, I'm estimating about two quarts, will i need more?

Thanks

75w90 synthetic. It will take a little more than 1 bottle.

I believe my 84 126 is 1.1 or 1.2 quarts to fill. I don't have my FSM on me but I believe yours is 1.2 quarts. So yes, 2 quarts is what you need.

I use Mobil 1 Synthetic 75w-90. As always it is up to personal preference if you use synthetic or not.

I also remember hearing that if you switch to M1 syn, you should do another change 1 year later because it really cleans things out.

One note- When you do the change make sure you remove the upper bolt first, then the bottom one. You don't want to drain it and have no way to fill it.

Have fun! :D

I just did mine this weekend. I HIGHLY recommend getting a pump and hose for the bottle...I only had the pump, and it was quite the contortion act. I am known to do things illogically, though..:rolleyes:
Not sure how the SDL is set up, but even with the long, pointed tip bottle, I wasn't able to reach the filler hole because my exhaust was in the way.

I had a pump when I changed my 126 but I'm pretty sure I got one of the two bottles up there and dumped oil in without a pump. But I would get one just to be safe.

Here is a nice write up courtesty of dieselgiant- http://www.dieselgiant.com/mercedesreardifferentialfluid.htm

The W-126 doesn't require a hose or a pump. The clearance is sufficient for the pointed tip on the Mobil-1 bottle. The exhaust is on the opposite side.

Nice. I was a little surprised that my drain and fill plugs were on opposite sides of each other. Oh well. I've got some time before I have to deal with that again. No blow torch needed either!

What diff fluid would be recommended for the locking diff in my 300D?

LSD? See here:
http://www.peachparts.com/shopforum/showthread.php?p=2041592