Author Topic: centre diff that has been leaking for years and squeaky noise heard at 100km/h  (Read 386 times)

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Offline user2154

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With the squeaky noise that I have been ignoring for years starting to get uncomfortably louder and not wanting to be one of those broken down on the Auckland motorway I finally decided to investigate this problem.

I have had a leak from the seal when the centre driveshaft front CV mates to the centre diff for as long as I have owned the vehicle but it only drips (a tiny bit) if I park facing up hill so I have managed to get away with it now for many years now.

To get to the centre diff fill port requires removal of the CV heat shield which requires removal of the much larger chassis heat shield which requires removal of the exhaust mid section from the downpipe back, which requires removal of a skid plate. The only hard part about this is the exhaust removal just due to the corroded fasteners. This is comfortably achievable with the car on ramps at the front and a rubber mat to lie on.

By some miracle I managed to get all 6 of these bastards loose without rounding a nut. I sprayed them yesterday with CRC marine 66 and then again before removal.

There are two exhaust clamps about 1.5 metres down from the cats which are easy to remove. I managed to break 3 of the 4 nuts loose without rounding but one was fastened too tight so I could not get the socket onto it square. This one I rounded and had to cut it with a hacksaw and then smash it with a hammer and chisel but that only took about 20 minutes. Centre section of exhaust removed.

After that I had a look at the driveshaft centre bearing and after 300k km it has excessive play. Hopefully this is the source of the whining / squeaky noise I can hear only at 100km/h. Here is the play in the driveshaft.

If I rotate the shaft a little there is a tiny tiny amount of play from the centre diff but I think this is normal. There doesn't seem to be any play from either the front or rear driveshaft CV but I have not yet removed the shaft from the vehicle.

front CV and leaky diff seal

rear CV

So I have ordered the new diff seal plus two new CV's and two boot kits, as well as the driveshaft bearing. The driveshaft bearing and CV boot kits are 034motorsports kits but I bought the lot from fcpeuro as I could not get the other parts from 034 (but I can get the 034 parts from fcpeuro).

So to remove the driveshaft you have to remove the entire exhaust so that has been done. It's a heavy bastard. Spray the rubber mounts with CRC 66 or some other lubricant from a can so you can easily lever them off with a screwdriver.

Upside down photo of my workshop for the last two days and the rest of the exhaust.

Next step is to remove the driveshaft but I think that can wait till next weekend or the one after that..
« Last Edit: April 22, 2018, 04:44:12 pm by user2154 »

Offline sfkarl

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I have a B6 3.0 quattro and replaced the output flange seal at the rear of the trans a few weeks ago. Yes there is a lot of stuff to move out of the way but the job itself was pretty easy!
Only 100kms but going through the service history the seal had been noted as leaking some time ago. When I drained the transfer case where the center diff is there should have been around 900ml of gear fluid in there. There was about 250ml or so. Wasn't dry at least. After replacing the seal and filling the housing the drivetrain felt a lot smoother right away. There was a lurch between acceleration and engine braking (auto trans). However, after a few weeks the lurch returned disappointingly. Maybe not as bad, but not gone away either.

For the Quattro IV system I know there is a torsen center diff and an open front and rear diff with traction control operated through individual brake application. Because there is no electronic or active control of the center diff, (entirely mechanical) should there ever be tyre scrub on very tight turns? Can a torsen diff only compensate up to a point and then a bit of binding occur? Or should this never happen?

If I drive on tarmac carpark with steering on full lock (left or right it doesn't matter) it sounds to me like a binding diff. I don't know if this is normal and acceptable.

Offline user2154

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I also get the tyre scrub at full lock but from what I read online this is normal.