I noticed this today when coming to a halt from highway speeds at a stoplight and then at a bunch of stop sign intersections from ~40mph after that.

Car is an '07 auto, only mod is a JLT CAI + xcal tune from reputable tuner. 4800 miles on the car.

When it is downshifting as I'm decelerating from 20-10mph there is a small "thunk" and then a larger "thunk" from 10-5mph. It's never been there until today. It doesn't jerk the whole car, but it is definitely noticeable.

I was stuck in traffic for about an hour on my commute home in 90ish degree weather (hotter than it has been) and it started about halfway through.

 

I've heard the clunk once. I drive an 07 GT auto as well.
The only time I heard the clunk was under really hard braking while exiting the highway from 90mph.

Pretty strange problem if it's continuing.

 

I wonder if has to do with G forces and the fluid. When I do used car checkouts(mostly high mileage stuff), you can tell if a cars transmission fluid is low by jamming the brakes and hitting the gas. If its low-a slight slip and THUNK.

 

It could be the 2-piece driveshaft and/or rear-end.

 

I would try taking the CAI off and Detuning it and see f the problem is still present. then if it is take the care in.

Richard

 

I used to have a similar clunk on an '82 Camaro Z28...in fact, it was par for the course.... just about everytime I came to a stop from about 40 mph (with a bit of hard braking involved) it would make the "clunk." I ended up putting about 60K miles on her before trading her in and I never had a transmission problem...
I know it doesn't make you feel better...but at least I don't think it's going to cause any serious problems.

I have heard it a couple of times on my '06 GT...but I remembered my '82 Camaro and dismissed it.

 

mine clunks too... i wouldn't say it's clunk though... more like thump. it depends on what tune I'm using... ie, what's the shift pressure in tune. i don't worry about it. i actually like it.

 

mine makes noises all the time.

 

My auto clunks and thuds all the time and since im out of warrenty i just keep telling myself it normal.