Mechanical rattle / clonking when shunting

[The Horse]

I've had my Chim since May and always struggled with the shunting when trying to hold a steady 30 or 40 mph. The clonking that you can hear / feel is not good and I had visions of the diff mountings being detached or the propshaft / driveshafts being lose or the UJs knackered.
I've just removed the exhaust system to have a better look and everything seems very tight. I can't feel any play anywhere. Any idea what might be happening or where any play can normally (if there is a "normally" ) be found.
It's a 1994 Chim 400 with a T5 box but I believe a GKN diff. The diff does not whine at all.
Here's the diff.

Any suggestions as to how to cure the shunting would also be greatly appreciated.
Cheers

[shake n bake]

I thought something was amiss with mine but it turned out to be a loose engine mount!
Certainly worth checking.

[OleVix]

I changed CV joints on each side, that helped a lot but the rest of my clock seems to be in the diff its out now

[QBee]

We are good on here for lots of things, especially advice on modifications, wheels, mirrors, tyres, and lots of engine stuff.

But some things I read I just think "take it to a man with 20 years hands on experience of TVRs and he will quickly and accurately diagnose your issue and suggest how to fix it".

If you don't mind a little drive from Suffolkshire, you could take it to Mat Smith (of Mat Smith Sports Cars) in Downham Market, Norfolkshire. Mat fits that description to a tea (milk, no sugar) and is a true TVR enthusiast - he even prepares and races a pre-serp Chimaera. 01366 386004 if you fancy the excuse for a little drive.

[The Horse]

Thanks chaps
I'll use a big lever and see if I can see any movement in the engine mounts tomorrow.
OleVix, could you feel any slack in your old CV joints before you replaced them ? Are you doing your diff yourself or giving it to a specialsit ? Is it a GKN or BTR ?
Thanks QBee for the Matt Smith recommendation. Personal recommendations are certainly the best and I'll get in touch with him.
Cheers
David

[OleVix]

The Horse said:

Thanks chaps
I'll use a big lever and see if I can see any movement in the engine mounts tomorrow.
OleVix, could you feel any slack in your old CV joints before you replaced them ? Are you doing your diff yourself or giving it to a specialsit ? Is it a GKN or BTR ?
Thanks QBee for the Matt Smith recommendation. Personal recommendations are certainly the best and I'll get in touch with him.
Cheers
David

Yes slight slack but not much. It was enough to irritate me! The diff is a BTR and I'm doing it myself as I have my own shop and other specialists around me.... and because im in norway and none of the usual suspects are based here!

[QBee]

I too have a clonk a la derrière. Lots of banging in the clutch on 30+ tracks days may have something to do with it.

On a quick inspection Mat has detected some movement in the drive shafts/diff/CV joints when turning the road wheels by hand with the car up in the air, so it is going in soon for a full diagnosis and fettle, plus a service, prior to the start of the dry track day season.

Only a 150 mile round trip for me - worth every mile as he discusses everything with me fully and shows me what and why.

[The Horse]

I couldn't find any play in the drivetrain but did find that the offside front bottom ball joint has play so I've ordered one from Racetech. Should be here tomorrow.
I've booked the car in to Mat Smith towards the end of January so him to have a look and see if he can find the cause for the excessive "shunting" and resultant mechanical knocking.
Thanks for all the help.
David

[trev4]

If you are booked in to Matt's it might be an idea to get him to check the wheel alignment while its there, if it hasn't been done lately it will transform the handling

[QBee]

trev4 said:

If you are booked in to Matt's it might be an idea to get him to check the wheel alignment while its there, if it hasn't been done lately it will transform the handling

Spot on Trev, I agree. He has the latest Hunter computerised aligner, and also knows what adjustments to make to the standard set up to suit the driving you do (eg extra camber for track use).
And as an added bonus, he is happy for you to watch and discuss what he is doing. Top bloke.

[taylormj4]

I've had the clonking with shunting thing for around 10 years and had various goes at resolving it. The diff bushes have been replaced and the UJs. The team at Forza West had a look at it some years ago and found the flywheel was loose (probably from a clutch change not being done properly by a different garage in Cardiff). However, that did not remove the clonk so they concluded that the play was probably in the gearbox and further investigation would have been through removing and stripping the gearbox, which would obviously have been pretty expensive.

So I left it and it's not got any worse, just makes driving a little less pleasurable than it could be.

[QBee]

Mine doesn't shunt, so it's not a case of "they all do that, sir".