Help! Nasty clunk from rear??

[GTVeloce]

Took the 75 to Bussellton this weekend and partway here I began to get a really bad clunk from the rear. It only occurs during torque changes in gear. I can rev the engine in neutral no problems. Select first and drive away all good. But clutch in causes a terrible clunk from the T/A. Same again when I release clutch in second. It does it through all gears. Feels like something whacking underside of car.

Will also do it with torque changes in gear I.e. on off throttle. Once in gear and on constant throttle, the cars runs fine. There were no obvious prior indicators.

Have got underneath as best I can and everything looks fine. Engine mounts (3), gearbox mounts (3), t/a bush, donuts, centre support.

Only thing I did find was grabbing the right rear wheel and push/pulling produced a bit of a clunk. Could it be right drive shaft where it meets diff? I kind of thought any problem there would show up more often like during corners.

Any thoughts? I'm still driving the car (carefully) but would really like to diagnose problem in case I'm doing more damage.

Thanks.

[Robert. Dale]

My guess is that one of your gearbox mounts has separated and is allowing the gearbox to move and knock on the A frame or the exhaust.
It would very hard to see unless you got right under the gearbox and used a lever to try and move either side up or down.
I have has this happen on the track.
Regards, Rob.

[Mick A]

+1 for gearbox mount. Probably R/H side as it lifts with the torque of the driveline.

[GTVeloce]

Thanks guys, I appreciate your responses. The gearbox mounts are the hardest for me to see so could very well have died and still look acceptable while lying underneath.

Obviously I will be putting extra strain on other mounts while driving it like this but do you think two more days of careful driving will do too much damage? Once I'm home I can pull it apart.

[Neil Choi]

Me three I have had that happen too.

A cheap ass way to fix can be to drill a hole (8mm) through the mount and stick a big bolt through it, if you don't have one handy.

[Mick A]

The bolt through the mount trick is good for a race car but not good with road cars as it can cause excessive vibration through the body of the car.

[GTVeloce]

Thought I should close this thread out. It was the right hand gearbox mount. However, there was nothing wrong with the mount. The two bolts that hold the mount to the gearbox however had come completely off! Not sure how but I am assuming the mug who put it back on last time didn't torque them correctly. I was having problems with the clutch slave and was undoing things in an attempt to remove and replace it so maybe I missed something. Needless, everything has been given a good once over and she drives well again.

[DHDamo]

Just had this clunk fixed on my gtv (gear changes/power on and off etc) - as suggested by the knowledgeable forum it was gearbox mounts (driver's side completely busted). Thanks again for all those who share their knowledge. DB