Large Thud under hard gear change

[agent_audi]

There is a loud clunk/thud that comes from the rear of my ABY, it only happens under hard acceleration, or coming off throttle instantly at high rpm.

I believe its either the rear differential or rear right CV joint and there may be some play in the driveshaft, hence the clunk is the shaft trying to catch up with the transmission once the clutch has been released.

Anyone have this problem before or any ideas how to check or solve the problem

many thanks

chris

[s2_wot]

Diff mount?

[agent_audi]

Thats one of the things i have on my check list for the weekend. I hope to god its not the diff cant afford to replace that.

[Error404]

could be the rear diff mount has given up or incorrect backlash adjustment in the rear diff.

[s2driveruk]

another vote for the rear diff mount(s)

Alex, any details on how to reduce backlash on the diff...shims i presume?

[Jamo]

Rear diff mount, had it on my old Coupe until I went for a powerflex mount.

[Error404]

I need to do mine, not had time since I took my diff off rolleyes:
There are shims behind the outer races of the diff bearings in the casing and the cover.
You have to press out the races and redistribute the shims between the two sides to adjust the backlash against the pinion. You start off by checking the float between the races without any shims in place. then add the pre-load spec (something like 0.25mm - in the factory manual somewhere). This gives you the total shim dimension. Then you have to distribute shims to this overall dimension between the two races to achieve the right backlash specification.
I've got a PDF of the factory proceedure for it somewhere on my PC at home if you need

[s2driveruk]

sounds complex so probably something for me to worry about on my return from the Ring providing the car gets round it in one piece

WOuld be good to sort it out though...plenty of lash in mine though. does that mean there is also a similar procedure for the front diff too?

[Error404]

yup! not a 5 minute job, similar story for the front diff too - you'd need the box off for that I'd guess

[s2driveruk]

Alex - any chance you can post the shim details?

[Error404]

PM me your email I'll send you some info mate

[DarrenM]

I've had this on mine for a while too, i've kinda adapted my driving style and feather the throttle to suit. I really do need to get it sorted too if you've got the shim details.

[Rusty]

If the diff mount looks OK then check that the bolt is tight - that was the issue with mine, recently.

[Lloyd]

I suspect it's your front mount on your rear diff that's the culprit. The diff snub mount.

[moggies]

I had the same thud with a kernackered rear subframe bush on my 80q