Hi, I own a 2004 Cadi Deville with 100k on it. Once in a while while driving the transmission will make a bang when shifting gears. I have noticed if I pull of the road shut off the engine and let the computor reset itself it shift like new no bang for a hour or a day or a week but then bang it does it again. what is causeing this and should I be worried

 

Welcome to the Cad forum!
Sounds like you have some codes being set that need to be retrieved in order to correct the problem. If there are any codes set that would effect the operation of the trans, the PCM will put the trans in a "Fail Safe" mode, which includes raising the line pressure of the trans, creating the harsh shifts. Turning the key off clears those codes temporarily. Once the PCM sees the problem again, the process will start all over. My suggestion would be to pull the codes, and see what the PCM sees as a problem, and then we can go from there. If you have an AutoZone close by, you can take the car there and have them scan it for free.(other part places may do this, too). Be sure to get a print out, or write down ALL of the codes they get.
Once we have some codes, we can zero in on the issue.