Car feels like it jerks and makes a clunk noise at low rpms

To rule out the tune, put the stock tune back in and go for a drive. If the jerking clears up, contact the company that created the tune for you and get a hold of their customer service group.

It could be the rear gear install; who did the installation? Drive shaft reinstall tight? Maybe the driveshaft is loose from the re-installation. Take it back to who ever did the gear install and have them re-check everything.

My car will clunk every once in awhile during rush hour crawling stop and go. I have no tune installed at this time.

I have a 2004 mustang GT auto and it does the same thing every once in awhile. When the RPMs drop from around 3/2 down to 1 it will jerk a little. No gears installed or tune yet.

My 2011 automatic has always gave a little nudge at a few miles per hour when coming to a stop. I thinks it normal, but mine doesn't have any sounds.

Thanks for the advice. I will call the guy who installed the gears. He did a good job but I was concerned about the jerking/nudging.

I was reading that the noise might go away if I buy a new drive shaft. Maybe this will be my excuse to get get one. I didnt think I would need one since Im not a speed demon but they say the ride is smoother.