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I have a 1997 Honda Accord with automatic transmission and about 150K miles on it. Frequently when I accelerate to around 3000 RPM or higher, and then let go of the gas pedal, about 1 second later I will hear a thump/thud noise from the rear of the car. It doesn't always happen when I let go of the gas pedal, but it is more likely to occur if I have accelerated to 3000 RPM or higher.

You can hear the sound in this video - wait until the very end to hear it.

I recently took my car to my mechanic and had him look at a few issues including this thud/thump noise. He called me and reported his findings. He said that the thud/thump noise was just due to the transmission getting old, and it isn't a problem for now. But he said that down the road I'd have to either get the transmission replaced or get a new car.

When I went to pick up the car, I tried to have him clarify what he meant by "down the road" - did that mean one year or several years? He changed his mind and said it wasn't a problem at all, and I didn't need to worry about replacing the transmission or getting a new car. He said I could continue driving the car for several more years.

Based on my description and the video, does anyone have any idea what is causing the noise? Is it indeed due to an old transmission and there's nothing that can be done about it, and it won't be a problem short term or long term?

  • I think this might be a good time for a second opinion. Do you have another mechanic with whom you can check the problem? – fred_dot_u Oct 10 '18 at 12:11
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I took my car to the dealer and got a second opinion. They heard the noise and thought it might be a problem with an engine mount, but later they ruled that out. They said it's a problem with the transmission - the gears are not shifting correctly when dropping from 3rd to 2nd gear. They said it's not a big deal given the age of the car. If the problem were to get worse, the thumping might become louder or the car might fail to shift gears, but that might not happen for several more years. So I can just keep driving it and live with the thump.

EDIT: The thumping may be getting a bit worse, so I have changed my driving strategy recently. I used to always drive in D4, but now I am driving in D4 only on highways and D3 the rest of the time. I still hear thumping once in a while, but it doesn't happen as often as when I always drove in D4.

  • If you accelerate then close the throttle , an auto trans is very likely to up-shift, not down-shift. That is go from 2nd to 3rd. An auto trans will down-shift ( eg. 3rd to 2nd) when the accelerator is pushed ( open throttle). However a poor universal joint may "thump" with throttle opening or closing , or both. – blacksmith37 Apr 5 at 0:21
  • Ah, the invoice says “Thumping noise heard going from 2nd to 3rd gear”, and I thought it was a typo, but I guess not. Is a universal joint part of the transmission, and can it be easily replaced? – pacoverflow Apr 5 at 2:44
  • For rear wheel drive there are usually 2 U-joints, one at each of the drive shaft, not difficult or time consuming. I never worked on front wheel drive but there must be some U-joints – blacksmith37 Apr 5 at 16:11

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