Non LSD Rear Diff Question

[acat2002]

Now that spring is on our doorstep here in New England, I'm unearthing the coupe from its winter cacoon and attending to some routine maintenance.

One of the items I'm addressing is changing the rear diff gear oil. I have a non LSD rear diff and haven't been under the car in a while so wanted to gather some quick opinions on your experiences with different gear oils and drain/fill procedures. I recently saw a thread involving different types of oils, but was more interested in the don'ts rather than finding the race-spec gear oil for my pampered automatic.

-Any time-saving shortcuts or special workshop tools used for adding new oil?
-What's the middle-of-the-road spec for gear oil for a non-LSD, non-track, unmodified, stock automatic?

Funny, the blue books don't really help in this regard (or maybe I'm looking in the wrong section).

 

[steve in reno]

ACAt
You seem to be confusing the issue.
Your differential is not, and has nothing to do with, your automatic transmission.

To drain and replace your diff oil.
Take for a drive to warm up the oil in the diff.
Remove drain plug at lower plug on diff. RE-install plug after draining is complete.
Remove upper plug. Install new oil and replace plug. Tighten plug, no torque #, no sealant/tape.
I installed 75-90w redline oil to mine.
No special tools needed to drain. However you will not be able to pour oil into diff, limited room. Will need to be pumped into diff, hand pumps are very cheap. Try harbor freight.

steve

 

[x_atlas0]

Indeed, very similar to manual trans filling. Hand pump helps a ton, but it still ends up being an excellent way to improve your hand strength, if you catch my drift.

 

[acat2002]

ACAt
You seem to be confusing the issue.
Your differential is not, and has nothing to do with, your automatic transmission.
steve

I guess I was trying to suggest that with an automatic transmission, there is no need or expectation for aggressive performance out of the rear end. Conversely, if I had say a 5spd CR w/ modded 3.5, maybe I'd consider the need for some more robust lubricant in the diff.

thanks for the advice on the hand pump. Maybe I'll let the oil container bask in the sun for a while so it flows a little easier through the pump?

 

[steve in reno]

ACAT
Sorry, didn't mean to snippy.
I would still use the same lub I recommended for your drivng needs.
i installed a 3.07 lsd from an E23, that is as quiet as a new diff 2 years ago.
steve

 

[bill]

Before removing the DRAIN plug and draining the oil, you should make sure the FILL plug can be loosened and removed.......!

 

[acat2002]

Thanks guys - all good advice.
The one other question I have (and it may turn out to be very obvious), but what size bolt/allen head size for the fill and drain plugs?

Reason I ask is that I have access to a garage with a lift, but need to import my own tools from my own shop. Don't feel like toting everything under the sun and wouldn't dare ask another mechanic to pillage through his tools!

I'm looking forward to getting her out of the garage again!

@steve - after reading my original post, it does read as though I'm asking about what gear oil to put in my automatic, so no offense taken. Regarding swapping the rear diff. - I was considering a 5-spd conversion last fall and if I ever do go through with it, the rear diff will definately be replaced with an LSD at that time.

 

[knucklehead]

Before removing the DRAIN plug and draining the oil, you should make sure the FILL plug can be loosened and removed.......!

A good maxim on any BMW diffy to be sure Bill!

IF you do wish to change out the oil a standard 80wt gear oil is the preferred fluid but unless it's seeping or you hear the pinion bearing whining as you motor along...
perhaps refer to the other even older maxim " if it ain't broke don't try to fix it? "

Jesse

 

[PaulinPa]

Drain plug 10mm allen.