2007 colbat bumps when accelerating from 50 mph to 60 mph when passing someone. Has no other problems when shifting at other times. Also does not bump if pushing pedal to floor when passing. Dealer has replaced valve body but problem still exists. Has anyone had this problem and had it repaired. Help !

This one is a mystery....it only bumps when passing, never during normal shiftsparticularly under heavy acceleration? Considering the dealer has looked at it for you, unless someone that frequents this forum that has had this problem before and fixed it can come to your aid, I don't know how to help you over the computer -- sorry.

Just thought I would give everyone aheads up in case you run in to this problem. Dealer has replaced the transmission control module and so farseems to havefixed the problem. Thanks

I think they had a lot of those parts in 2007 Cobalts or something. Mine did the same thing.