2005 Impala

My 05 Chevy Impala has had an ongoing problem with the transmission.

From a dead stop the first gear is smooth,but when it shifts to the next gear, there is this thud and again another thud when it shifts to third gear.

I’ve had it in the shop a couple of times, to no avail, as they can’t figure what is going on!

The problem comes after the car has been driven for awhile. I can park the car for a while and go somewhere and it’s ok.

Thank you.

You’ve had it to what kind of shop? You need to take it to a transmission shop, to people who have the expertise, tools, and experience on transmissions, who can fix it.