My brother got a car from a used auto dealer. When you give the car gas it will roll but if u want to accelerate quicker by pressing it will climb to like a thousand revs and them slam and then carry on. And it shakes before kicking, Went to the place he got it from and they said replace all motor mounts $800. Now I have a car with bad motor mounts and I don't have similar issues. Now 2007 chevy's seem to have a issue with transmission slips according to scarce reviews online. The company provides a powertrain warranty but refuses to fix the transmission or look at it because they are saying it's mounts. What could this be as the slamming and shaking has gotten worse. My brother is a OTR Trucker and I'm trying to help out. Car always kicked from beginning but not noticeably until recently. Any help is appreciated.

 

Try getting the car scanned for transmission error codes at an auto parts store? Could give you some ammunition to go back to the dealer with.