I have a 2008 impala that I have serviced and maintained regularly. I recently hit a pot hole with the right front tire and brought the car into the dealership to check out the recent noise coming from the front (very slight grinding) in the front and the fact that the car just started sticking when in reverse. The mechanic is indicating that the transmission needs to be replaced or rebuilt. Is this likely since I have not experienced any problems with the transmission in the past other than the people who do my oil changes indicating that I should change the transmission oil. I have had no problems with the vehicle while driving or with the automatic gear changes and no odor of any burning or evidence of greater noise while the car is in neutral. If the mechanic indicates that the transmission needs to be rebuilt should I ask for a list of the parts to be replaced and ask for these parts? If he refuses to give these parts, should I have it towed somewhere else for repairs?