vl tailshaft/diff problems

[88-SERIES200]

I have a problem with my vl. when the car is just rolling then you put your foot down there is a metallic sounding clunk from what sounds like both the tailshaft and the diff. this also happens when you are cruising then have to take your foot off the pedal suddenly. (such as if you were to have to put the brakes on because a car has pulled out in front of you off a street. i took it to a mechanic to take it for a drive and to put it up on the hoist and he said it seems to be a combination of play in the tailshaft and backlash in the diff. they quoted through another place they go through $350 to replace the centre bearing and i think uni joints. this is without balancing the shaft or fixing/shimming the diff. I dont think this price sounds too bad but i would like some advice on how much this should cost as i havent had to get this done before. I would very much appreciate any help. thanks!

[jatsvl]

first I would check exhaust hangers, they are a very common problem when one breaks the rear muffler (resinator) bangs on the side of the fuel tank or rear panhard rod, also if you have an aftermarket exhaust or sports exhaust will result in this same problem aswell.
secondly I would check the trans mounts aren't sagging and/or broken, (an easy way to check is lay next to the car and look at the backside of the trans crossmember the lowest part of the trans should be about an inch above the crossmember any lower the mounts are stuffed.) if this is the problem shop around I got 2 mounts for the price of 1 and had change, some places (repco) will charge you alot more for left and less for right as they are slightly different.
I have heard of the clunk on acceleration but not on deceleration which makes me believe it could be one of the above, but if it sounds like a church bell, go below,
$350 for centre bearing and unijoints is not to bad if you are sure that is the problem, keep that quote.

[88-SERIES200]

Ok so i took the car to a workshop last night and got it up on the hoist again. the centre bearing and cv are pretty much done but the uni joints seem fine. but im just going to replace them all at once. Also i checked the crossmember as you said and it look a bit twisted like someone has reversed over something and hit it. so one of the rubber mounts is completely broken off. so now im out looking for a crossmember and 2 mounts. 2nd hand but in good nick. any idea how much i can pick these up for? and also would it be a better idea to find some brand new mounts to use with a 2nd hand x-member.