Clunk from back end on a 500

[eng622]

Power off then power on poduces a slight clunk which I'm pretty sure is in the driveline. Could this be UJ's or something else

[Johno]

Prop shaft UJ
Driveshaft CV's
Diff bushes
Wishbone bushes

There is always some shunt, but if it something that has developed it's most likely to be one of the above IMHO.

[clive f]

could be loose bolts on the cv joints, or worn diff bushes?

[Adrian@]

Check the bolts on the rear diff mounting bracket..... for being too short and stripping the threads in the diff casing.
Adrian@

[OscarT]

What's in your boot?

[V8 GRF]

Sticky valve in a rear shock?

[red griff roger]

I think there is always a small clunk. Only worry if it is new/getting louder/more clunky. If you jack up the rear, you can move the back wheel through a degree or two when in gear. All builds up from play along the drive train.

[GreenV8S]

red griff roger said:

I think there is always a small clunk. Only worry if it is new/getting louder/more clunky. If you jack up the rear, you can move the back wheel through a degree or two when in gear. All builds up from play along the drive train.

An inch each way at the tyre is about normal, by the time you've taken up the CV, diff and UJ backlash.

[groucho]

I had a clunk that got worse. Ended up having a new dif.

[eng622]

The possibility that it is the diff worries me on the car in question. It is one of 7 I have test driven that are/have been for sale. All the others were quite at the rear as was my V8S. I'm being cautious as it could prove expensive unless the seller is prepared to fix.

[DustyC]

Might just be a a broken bracket on the diff. Mine was.

There is an easy fix. Just keep the power on and don't let it off!

[red griff roger]

Ah. If you haven't bought it yet and are very worried, then there is a very easy fix.

[mikeb]

I have a similiar clunk, had a poke around on the car and was able to move the entire diff up and down with a pry bar and the allen bolts were moving on the diff carrier.

Obviously the loose bolts causing the heavy clunk under power, but also had quite a bit of play in the prop shaft without it actually moving the wheels! - diff worn?

Back to the bolts though, can these bolts be done up without removing the exhaust?? It all looks extremely tight on space up around the top bolts.

It looked to me that the allen bolts sat on one side and then went through the diff carrier and the diff housing and then a nut holds the bolt on the other side??

Is this correct or does the allen bolt screw into a thread in the diff casing itself? If so could the threads be worn or stipped? Coult the allen bolts be replaced for some proper bolts??

MikeyB

ps. my cars a 4L precat not a 500

Edited by mikeb on Monday 22 October 18:57

[clive f]

mikey, I appear to have the same as you, whilst down at Dulfords a while ago, I asked the mechanic, a little bloke called colin, about a clunking noise when taking up drive, with the car up on the ramps he showed me that the diff bushes were all knackered, which was suprising as these were replaced by the previous owner only 2 years ago, we then found that the reason for the bushes being knackered was because the front of the diff is secured by 4 allen bolts to a support plate, the diff casing contains a thread, and then a lock nut is screwed onto the back of the bolt, the mistake being, that the allen bolts were torqued up, but then when the locknuts were tightened up the bolts slackened off slightly because the bolts were not held whilst the locknuts were tightened, this then allows the diff to twist slightly when under load, and the amount of movement is greater where the bushes are, as they are further away from the centre of the diff.
Another job for the winter

[wintrading]

I got the same problem. I bought new dif bushes. But can someone explain me in very simple english what causes it? I do not understand the words used by clive. From amsterdam and my technical english is not so good. What should i check? I am going to replace the worn bushes and what else?

thanks

[clive f]

nothing else to replace, make sure that all bolts tightened properly.

[mikeb]

I have had the bushes replaced a month or two ago. Can you tighten the allen bolts in situ without dropping the exhaust?

MikeyB

[spend]

They are hard enough to torque up even with the exhaust & prop shaft out of the way IMHO.

Dave

[clive f]

you`ll get at the bottom two, but not the 2 at the top, exhaust will need to come off really.

[DarkMatter]

My '96 Griff 500 clunks too (I assume it's the diff) when accelerating and releasing the clutch quickly. I took it to an 'indie' TVR mechanic in the Hants/Surrey area who said the diff bushes/bolts are fine and not to worry about it. Well, I do worry about it. So, if the bushes are OK and the bolts are all tight it must be something internal to the diff which causes the clunk - can someone who understands diff internals explain what exactly could that be? Thanks.

b.t.w. the clunk only occurs when accelerating and not on the overrun.