Rear diff fault?

[audinut]

Agreed they all do it. Put it on on tarmac they try to steer the difference is instantly noticeable.
Mine did it loads when first got it. Combination of geometry being out and shot tires.
However it still does it when getting on my drive slight incline at 3/4 lock.

Hmm ok my last one didn't do it ?

My geometry is bang on and i have brand new tyres with about 50 miles on them

gonna put it on the ramp monday to investigate

[hashluck]

I have been reading up a lot on the Diff Lock for one of my ABY S2s thinking I had a fault and now reading this thread and thinking I may not. First of all the write ups on here and the Diff Lock 101 on quattroworld are brilliant so thank you to all the contributors.

I have been shaking down the S2 I purchased which has basically not turned a wheel much for 10 years. All fluids and cambelt etc changed BUT tyres are still 10 years old and rather square. Everything except the AC works and the car drives very well (allowing for the hard square tyres). An occasional 'clack clack clack' when cold which I think is a pulley or something - seems to be external to engine at least.

One test that did not go so well was for the Diff Lock - the vast majority of times it works as expected but 2 or 3 times now the following has happened. Press Diff Lock Switch, green LED lights up on switch, ABS Off light comes on on dash, all as expected. Attempt to drive off and it is if you are trying to do so in 6th gear, I now realise car is crabbing badly and it actually feels like the ABS is pulsing on one of the rear wheels (but it cannot be as it is OFF).

Now, I am thinking that when this has happened it has coincided with me pulling out of my drive (sharp left or right turn) which reads like a bit of a no-no with the Diff Lock engaged? Combine this with the very dodgy tyres and I may be asking too much?

I will check the one way valve, vacuum lines and actuator but thoughts from the assembled brains here are appreciated.

[Tractor Dave]

Sounds like its working to me. Diff lock should only be used in mud, snow or loose gravel conditions. You can test on tarmac but only in a straight line.

[hashluck]

Thanks Dave. I should have added that when it works it also shuts off as expected above 15mph

I also do think this fault condition though may also have occurred in a straight line albeit on smooth tarmac and I have never experienced it on any of my other quattro past or present. When it does happen it also will not clear itself, you are basically not going anywhere even when you have straightened up as best you can. You have to stop, into neutral, turn off Diff Lock and hopefully proceed OK. Diff Lock does not always manually turn off but will after a couple or few goes

I am not going to push my luck with it, especially as the tyres have thrown a possible cause into other mix as well as the on steering lock part. It does sound like I have a system which will get me out of trouble in situations it is designed to be used in.