Big Clunk Noise/feel Of Shifting Weight From Rear

[sl33py]

I've got a R33 GTST stock power upgraded clutch and Xtreme light flywheel. Ever since I upgraded the clutch and lightflywheel, sometimes when I change up gears I get what feels a heavy weight shifting around. ie when I shift up, there is that slight moment when the car feels like it's floating forward a bit before you get back on the gas and as soon as I do, I hear something in the drivetrain go clunk/clack and a very certain weight shift backwards, giving a thud I really dislike. I realise a light flywheel and heavy clutch (mechanic says its good for 300rwkw) will make the car a bit harder to drive, but this clunk happens at really random times and various amounts. I've experimented and can't reliably make it happen. I want to eradicate this from the car.

Can I get some suggestions on what to check out? Gearbox or transmission mounts? I think the clutch is installed correctly, I just reckon because it grabs much harder and in combination with the flywheel, it's showing up some weaker part of the drivetrain or mounts or something. One friend said it might be the centre drive bearing (not sure what that is). I am thinking of going back to the stock flywheel anyway, but I want to get rid of this sh1tty movement/slack before making that decision rather than just covering it up again. When it happens, it basically feels like there's a heavy sub in the back sitting on a slipper surface and free to move backwards and forwards about 5cm - you can imagine how annoying that is on gear changes with any momentum built up

Oh and since I know it'll be suggested - I really don't think it's just my driving cos about 60-70% of the time it's all smooth and easy, and then on a gear change exactly like all the others I do, it'll go ..... *CLUNK!* and I feel the thud from the rear. And I can't for the life of me figure out how those gear changes are different from all the other fine ones I do.

Edited December 5, 2007 by sl33py

[sl33py]

Noone?

[Duncan]

yeah start with the gearbox mount and diff bushes, if they are stuffed the box or diff can move around

subframe bushes as well they can cause a clunk under power

backlash in the diff (but if you haven't changed the centre probably not)

and finally, the thing it was on mine, stuffed centre bearing on the tailshaft.

[sl33py]

Cool thanks, will get them checked out. I just had the subframe bushes replaced so shouldn't be them. Hope it's something cheap