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Re: 200q differential leak

-----Original Message-----
From: Don +ACY- Lori +ADw-dell+AEA-pangea.ca+AD4-
To: quattro+AEA-coimbra.ans.net +ADw-quattro+AEA-coimbra.ans.net+AD4-
Date: Sunday, March 28, 1999 9:23 PM
Subject: 200q differential leak

+AD4-had passenger side rear tire off today and noticed leak running down
+AD4-differential.  also looked like some of the leak sprayed around the
+AD4-same general area.
+AD4-anyone had to replace seals in the rear differential.  is it a big job.
+AD4-any special tools required.

Hi Don+ADs-

    I replaced this seal on my '91 200q last year. I have attached a +ACI-How
to+ACI- I posted on the procedure I used.


Fred Munro
'91 200q  271k km

    I just put a new bomb in the '91 200q yesterday and replaced the right
rear diff seal today. The brake applications +ACI-in reserve+ACI- have increased
from a puny 1 to 30+ACE- The bomb replacement +ACI-how to+ACI- has been well covered by
other listers, but I thought I'd throw together a +ACI-how-to+ACI- for the rear diff
seal before the aches and pains vanish. Thankfully only the right seal was
leaking - the left is dry as a bone. Changing the left is complicated by the
exhaust system, heat shields, diff lock, and the fact that the seal is the
size of a dinner plate ( OK,OK, I'm exaggerating - it's the size of a
saucer). Sorry, Geo, you're on your own with that leaking left seal+ACE-

Rear Differential Right Axle Flange Seal R+ACY-R

1.    Jack up and safely support the right rear corner of the car. Remove
the right rear wheel.

2.    Remove the cover protecting the bottom of the right half of the fuel
tank - two 13mm bolts +ACY- two 13mm nuts.

3.    Get out your trusty 17mm hex socket and loosen the filler plug on the
rear diff - it's to the rear of the right axle flange. Loosen both drain
plugs. If you cannot loosen the filler plug, all is not lost. You can fill
the diff through the axle flange hole once the new seal is in. You won't get
it completely full, but it should be close enough, particularily if you have
the right side jacked up high. Not recommended procedure, but better than
running an empty diff. If the drain plugs won't budge, just top up the diff
with 80W90 hypoid oil rather than giving it a complete change.

4.    Disconnect the e-brake cable at the caliper and remove it from the
caliper mount. Pull the rubber e-brake cable bushing mount (about 18+ACI- back
from the cable end) off of the metal body bracket so that the cable is free.
This is a really good time to replace that sticky e-brake cable+ACE-

5.    Remove the bolt that secures the rear inner bushing on the lower
trapezoidal suspension arm and drop the arm. This bolt also secures a tab
which holds one corner of the skid plate, so it is double-nutted. The outer
nut is 19mm, the inner is 17mm, and the bolt head is 19mm.
    This is required to release the inner CV joint and drop the half-shaft
out of the way.

6.    Remove the six 10mm triplesquare head bolts securing the inner CV
joint to the axle flange. DO NOT use a Torx driver on these bolts - they
take a special triplesquare driver. Make sure the driver is securely seated
by cleaning the bolt sockets and tapping the driver home with a mallet. You
may want to matchmark the CV joint and axle flange so they can be assembled
in the same position - this is not required but is good practice (IMHO).

7.    Remove the CV joint from the axle flange. This may take some doing if
the car is old - rust between the joint and the flange can bind the unit
together. I found a liberal application of penetrating oil to the CV/axle
flange joint, repeated blows with a 2 lb hammer via an aluminium drift, and
swinging the hub assembly outward ( the inner bushing is off, remember) to
pull on the inner joint when the slack came out of the CV joints finally
popped it off. Lower the inner end of the halfshaft out of the way. The
innards of the CV joint are now exposed, so try to keep dirt out of it - a
small plastic bag is a handy cover.

8.    Remove the 6mm allen head bolt securing the axle flange to the diff
carrier - it is located in the centre of the axle flange. The axle flange
can be held while removing this bolt by inserting two of the 10mm
triplesquare bolts and using a bar or large screwdriver slid between the
bolts to hold the flange stationary.

9.    In case you haven't lost as much oil as you think, put a drain pan
under the diff. Pull out the axle flange. Inspect the seal running surface
for wear and clean the flange +ACY- sealing surface.

10.    Measure the old seal position with a depth guage to determine how far
in it is from the outer rim of the seal seat. There is no inner stop to
position the seal - the Audi driver tool has an outer flange which hits the
outer rim of the seal seat and stops at the proper depth. My seal was seated
9/32+ACI- in from the outer rim. Pop out the old seal with a large screwdriver.

11.    Wipe the seal seat clean. Note that it is tapered partway in but
there is no inner flange to stop the seal from going too far. If you drive
too enthusiastically, you can push the seal right into the diff - I can
guarantee this will ruin your entire day+ACE- Drive the new seal in squarely to
the depth measured in step 10 above.

12.    Fill the space between the lips of the seal with lithium general
purpose grease. Apply a thin film of grease to the sealing surface of the
axle flange. Slide the axle flange back into the diff.

13.    Insert the axle flange securing bolt. This bolt is tightened to 10 Nm
and then tightened another 90 degrees. Half of the bolt head in my diff was
nicely painted white to aid in this endeavour.

14.    Bolt up the CV joint to the axle flange. It is recommended that the
gasket between the axle flange and the CV joint be replaced whenever the
joint is removed. The 10mm triplesquare bolts are torqued to 59 ft.lb.

15.     Drain and fill the diff with appropriate lube. The Audi specs call
for GL5 spec 90 hypoid oil. GL5 spec 80W90 hypoid is OK, as are GL5 spec
synthetic gear oils. It's a good idea to put antiseize compound on the fill
and drain plugs to prevent electrolytic corrosion between the steel plugs
and the alloy case.

16.    Bolt up the inner rear trapezoidal arm bushing (63 ft.lbs). Attach
the e-brake cable rubber bushing mount and attach the e-brake cable to the

17.    Before bolting on the fuel tank cover, it is a good idea to spray the
fuel tank seam with an anti-corrosion compound (Rust Check, etc.). It looks
like the cover is in place when the factory applies the wax undercoat, so
the area above the rear diff and around the fuel tank doesn't get treated.
Liberally coat anything that looks like it might rust.

18.    Bolt on the cover, put on the wheel ( torque the wheel bolts to 85
ft.lb please), lower the car, and motor on+ACE-

Some Comments on The Left Diff Seal (The Mother of all Seals)

    This thing is huge+ACE- It is literally the size of a saucer. Access is
hampered by the exhaust system which has to be loosened and pushed out of
the way. The Audi installation tool is a threaded rod and a large steel
washer the size of the seal. The rod is threaded into the diff carrier ( in
place of the axle flange bolt), the seal is positioned in the diff, the
steel washer slid over the rod, and a nut used to pull the seal into
position. This complicated procedure makes me suspect there isn't enough
room in there to swing a hammer, but since this was the low side of the car
I didn't get a good look.
    For those who want to build their own seal installer( Geo?), I measured
the axle flange bolt thread - it is a 8M x 1.25.
    Otherwise, the procedure for installing the left seal looks to be
similar to that for the right seal.

Fred Munro
'91 200q  261k km (no leaks, full of oil, ahhhh)