I have a 2009 Vert, automatic trans with just 7,200 miles on her. I bought the car 5 years ago and it had 2,800 miles on her when I bought the car.
I don't race or beat the car --- I drive it only in perfect weather and for show. Car has been babied since I have owned it. Not sure about the original 2,800 before I purchased it.

When I put the car in reverse, I hear a klunk as the engine engages the drive train.
If I have the transmission in sport mode and have the car in 2nd or 3rd gear, when I let off the gas I hear the klunk and then when I accelerate again I hear the klunk.
Doesn't always do it, but seems to do it more when the car has been running for awhile and hot.

If I drive the car in just DRIVE (not sport mode and manually shifting), it does it much less.

If this were an older car, I would say I have a loose U-JOINT.

Any Ideas what I should look at before I take it to the dealer for evaluation???

 

Don’t want to panic you but that was one of my earlier signs of my A6 going. Not saying that’s what yours is but just throwing it out there to maybe look into.

 

One curse of non-driven low mileage cars is that seals, gaskets and joints dry out from lack of use. It's fun to have an older low mileage car, but that sometimes comes with its own set of issues. That said, does the sound seem to be more in the rear of the car? My first guess (just a guess) is the rear end is having issues (maybe low gear oil or the oil needs replacing) .Would be better just to take it to your trusted mechanic rather than guessing.

Good luck

 

Could be loose axel nuts. My 07 was doing this when I bought it. A couple of new nuts properly torqued with some Loctite and the noise went away.

 

I'm not a mechanic but to me it sounds like there is some play somewhere in the drive train so when the trans down shifts when you are slowing down you hear that klunk as it downshifts into a lower gear under no load
You don't hear any klunk under acceleration when going from gear to higher gear --- but you do hear it when slowing down and the trans is downshifting and not under any load or when you're driving slowly in stop and go traffic and the car is constantly down shifting into lower gears under no load. Those klunks are quieter/softer --- but they are there.

The klunk is most noticeable when I start the car up and then put the car in reverse. I shift the car into reverse and you hear a very audible klunk as the trans slips into reverse gear.
Feels like something is loose or worn out in the torque tube/drive shaft/U-joint. I am 'OLD SCHOOL" so I don't understand how the torque tube works on these Corvettes.
I'd be surprised if it were a transmission or rear end problem with such low mileage, but anything is possible. I also don't know how the car was driven during the first 2,800 miles I didn't own this car.

Loose rear axle nuts are a real possibility. BUT, Wouldn't know how to check that myself
I guess it's a trip to the dealer and brace myself for a BIG BILL. Maybe it's just a loose nut somewhere in the drive train.

 

It could be a lot of things but check the motor and trans mounts.

 

What speed07 said. Easiest thing to eliminate is the rear axle spindle nuts. When the clamping load from the nut relaxes, there can be a clunk with change in torque sign to the axle/spindle.

5 buck part, Get the rear wheels off the ground, pull the old nuts, 34 mm socket and impact for that. Jacked up, you have play at the splines, push them back and lube the splines. I use motorcycle chain lube. Spray into the splined joint front and back side, works the splines in/out a bit. Put the car back on the ground, set parking brake to torque to 140 to 180 ft-lb (correct me if I'm wrong on that). Use new nuts, these nuts get torqued to yield limit. Blue loctite on the spline threads at the face of the joint. If you put it on the nut it will mostly get wiped off running the nut in on the long threaded axle.

If you don't lube the splines that can lead to fretting corrosion. Look that up. There are a couple of ugly pictures of that around here. Doubt your low-miler has that problema. The splined joint is a slight slip-fit, that is where the clunk can come from.

 

OP,
I had a similar problem and it was the axle spindle nuts causing the clunking noise upon acceleration/deceleration. I installed new axle nuts with red loctite and torqued to 150 ft lbs, then installed the used nuts on the axle as a jam nut (check nut?) behind the new nuts. Seems to have cured the problem so far.

 

Thanks for all the help. I'm recovering from back surgery so I can't do the rear wheel axle nuts check. I'm bringing it to my dealer --- but at least I have more knowledge and can speak to them intelligently.
I'm 90% sure it is the rear axle nuts and will ask them to check that first. With such low milage, and the car not being raced or abused it can't be anything major with the trans or rear.
I probably will ask them to change the rear fluid with the limited slip additive while they have it in the shop.

 

Took the car to my dealer. Had the 2 axle nuts replaced and a rear end fluid change.
Klunk is now GONE.

Thank you everyone for your responses --- particularly the ones that highlighted the axle nuts as the probable cause.
I would have done the job myself, but I just recently had back surgery so that job would have been impossible for me to do