Center Differential Fluid for 4000q

[EricNMN at aol.com]

In my '86 4k Quattro, the fill plug was fairly evident.  It uses a 17mm hex head as I recall.  I think there were two drain plugs or two fill plugs for the transmission/center diff.  The center differential and transmission use the same fluid reservoir.

Another list member made a suggestion recently - remove the fill plug first.  That way, if the drain plug won't come out, just re-install the fill plug.  BUT, if you remove the drain plug first and can't get the fill plug out, you have a problem.

A few more recommendations:

Use a lift - I did mine in the driveway and cursed the lack of space.
Wear clothes you can throw out.  Gear oil has a strong/unique odor.
Use a synthetic gear oil.  I SUSPECT you need GL-4 75W-90.  Confirm this before you purchase.
Use a pump to fill.  There is not a lot (NONE AT ALL) of room to tilt the bottle when you fill the case.

Eric Schumacher
96 A4 Quattro
86 4kCSQ (deceased)

Is there a filler plug for the center differential on the 4000 quattro?  The drain plug is evident on the bottom.  I have heard different stories that there is and also that it is filled through the transmission?  I dont want to drain it until I know for sure where to fill it.  If there is a filler do you have to remove the cat converter to see it?  Also what is the correct fluid?
If its filled through the Tranny you have to use a synthetic correct?  The Bentley book isnt that clear as to the diff. fluid for quattro versus front wheel drive.  Any help is greatly appreciated.