I have a well cared for 03 touring with 125,000 miles on it. When I do a downshift even with moderate power and RPM's I get a clunk noise from the rear when the clutch engages and the power hits the rear wheels. On a very high RPM / WOT upshift it sometimes clunks too. I'm pretty sure that I can feel and hear that its coming from the rear and not the transmission. I'm thinking its a bushing or mount for the rear diff or drive shaft. This has been happening for at least a year but recently its gotten worse.

Clutch was just replaced about a month ago and had no effect on the clunk. I had the tranny fluid and rear diff fluid flushed and filled around 75K miles so all the standard maintenance has been done. Synchros are in good shape and tranny shifts smooth.

If anyone has had a similar problem or thinks they know whats going on with my Z based on this description please let me know. Before I start throwing a whole bunch of money and parts at it with this many miles on it, I want to get an idea of what I'm looking at first.

 

I have an 06 base 46k miles. When I start the car and go into first and if I shift before 3500 rpm it makes a dropping (clunking sound) when I put the clutch in. It only happens when I first start the car though and it is only when I shift in first. IDK!

 

That's your differential. Have someone crack it open and check the ring & pinion gear set. May also mean you are low on diff fluid.

 

This happened to me twice....

Once about a month ago and once today...I was babying the car at first but gradually started driving more aggressive since the first time, then it happened again :/

Right after it happens the car drives perfectly, although there might be some extra rattle from the JWT clutch (but I may just be listening more)

Yeah and just like you it’s when roughing up the car....I have new redline fluids (Diff and Box)

But the clunk is FRIGHTENINGLY loud and violent....

The first time it sounded like the box, today maybe further back but really not too sure tbh, the first time I swore half my car would have been left on the road....

I hope this does not lead to a big dents in our pockets...

 

Op I would suggest first checking out the rear diff bushing. Mine was doing the same thing when my rear diff bushing was broken.

 

I'd bet that this is the issue. Check all your diff bushings, subframe bushings, and suspension bushings. If all of those are good, then crack the diff open.

 

Finally replaced all 3 rear differential bushings with urethane ones and it fixed the problem!