When I drive my recently acquired 2004 Mitsubishi Endeavor, I occassionally feel (by my foot), rather than hear, something hitting under the car. It happens while accelerating but mostly while decelerating. I am wondering what it could be. ALso, I noticed I have two different brands of tires on my car…paired in front and in back. Is this a problem? THe diameters are 1/4 to 3/8 in different.
With any luck, it is merely the exhaust pipe hitting the underside of the car, but if you are unlucky, this could be a symptom of bad motor mounts and/or bad transmission mounts.
As to the tires, the answer to your question lies in your Owner’s Manual. Assuming that this a an AWD Endeavor, the difference in tire diameters may or may not be within specified tolerances for the AWD system, and the Owner’s Manual should have the answer.
Try to get into the habit of using the manual for questions such as this. Those of us on this board are happy to answer questions, but if you have a problem on the shoulder of a road at 3:00 AM, the manual is infinitely more accessible than this board.
Another thought–If the tires are not within tolerances, it is possible that the sensation that you are experiencing is from the center differential, as a result of excess wear, because of unmatched tires. Read that manual, and get the vehicle to a mechanic for inspection of the exhaust and the motor and transmission mounts.