Questions and Answers
Thumping Honda
Q. I have a 1995 Honda Odyssey with a 2.4 L engine, fuel injection, 4 speed auto transmission, ABS brakes, power steering, AC, cruise, and 73,000 miles. I have a concern about the auto-transmission. When decelerating, a thumping can be felt when the transmission shifts from 2nd to 3rd or from 3rd to 4th. The thumping can be felt from under the car about where the engine and transmission are. This feeling seems to happen more going down hill. The transmission shifts fine (although rather hard) when accelerating. There is also no thumping or clunking when shifting between park and the gears while stationary. I recently purchased this minivan used and did not notice this phenomenon while test driving. The motor mounts and transmission mount appear to be in good shape. The CV joints also seem to be fine. I recently had all of the transmission fluid replaced. The fluid was pink/brown but not burnt. The fluid did contain what appeared to be a small amount of fine metal flakes. Can you think of what the likely cause of this thumping might be? Or is this a sign of a failing transmission?
Thanks
A. From what you describe, the transmission fluid seems to be okay and it's normal for some fine metal particles to be in the pan. In fact most transmissions have a magnet in the pan to keep them in the pan and not recirculating through the transmission.
It's hard to say without driving the vehicle, but I would have to look at the motor/transmission mounts. I believe the problem lies there. There is a quick way to check them. This takes two people so grab a friend to give you a hand. Set the parking brake, and for added safety, chock the wheels front and back so it will not move. Start the car and step on the brake. Put it in drive and hit the gas a few times, up to 2500 - 3000 rpms and back down, and watch the engine. If the engine seems to "stand up" and you hear the noise, then you have bad motor /transmission mounts. Do this in forward and reverse.
Also check the shield on the transmission side. The one that comes down from the fender. Often when the engine moves, the transmission can hit this shield and cause the noise you hear. The tolerance is fairly close to begin with and over time it can come in contact with the back of the transmission. if this is the case, you can put a bar between the transmission and the shield and bend it out if is metal, or if it's plastic you can remove it and bend it so you get the clearance you need.
