I replaced my transmission fluid, filter, and pan in my 2003 Sebring Sedan (it's an automatic, 4 cylinder). The transmission works fine, but when it downshifts from drive to second as i slow down it makes a 'thump'. Only when downshifting when I'm slowing down, not when I'm accelerating. It has the right amount of fluid in it. Anyone had a similar experience who knows what the problem might be?

 

There's a possibility the transmission computer is just relearning after the fluid change. The rough shift may go away after a few days of regular use. If not, take it to a transmission shop and have them read the codes. It requires a sophisicated code reader.

 

Yes, I came to the same conclusion after reading about similar problems with other make cars. unhooking the battery for a few minutes disengages the 'brain' so it relearns the settings, so I'm going to do that and see if that's all it needs.