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I drive a 2007 Toyota Rav4, and it bucks / jumps in reverse when backing up a steep hill or accelerating on flat ground. When I first noticed the problem, I was backing up an unusually steep hill, so I had never put it under that kind of load before.

Here are some more details about the problem:

  1. It only happens when the engine / drive train is loaded enough (doesn't take much acceleration up a hill, takes a lot on flat ground).
  2. It only happens in reverse - you can strain it as much as you want in drive without this happening.
  3. The bucking is quite severe and seems to be coming from the front passenger's side of the vehicle (by severe I mean it feels like the front end jumps off the ground).
  4. It sounds and feels like a gear skipping a tooth.
  5. If you keep your foot planted on the accelerator, the bucking repeats immediately and indefinately.
  6. The acceleration is stunted every time it bucks (which is why it feels like a gear skipping a tooth).
  7. I first noticed it not too long after changing the transmission fluid and filter (but, as I said before, I had never put it under that kind of load before, so I don't want to implicate the transmission fluid right off the bat).

Here are some more details about the car:

  1. All Wheel Drive.
  2. Base trim level.
  3. It has roughly 115,680 miles on it.
  4. Four cylinder "sideways" engine, so it has a transaxle, not a front differential.

Here are some details on the transmission fluid change I did:

  1. When I changed the trans fluid, it was dark brown and there was a lot of metallic sludge in the pan.
  2. The method I chose for changing the fluid was three drain-n-fills and a filter replacement.
  3. I used official Toyota WS ATF, and installed an OEM filter.
  4. ~7-10k miles after that fluid change, the trans fluid is still full and looks good.

I would like to know if anyone has experienced this situation in any similarly configured car, and what the root cause ended up being.

Thanks in advance!

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  • Have you watched the front wheels when this happens to see if anything strange is visible?
    – HandyHowie
    Oct 30, 2023 at 8:13
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    Pop the hood and observe the engine from the driver's seat as you perform the maneuver you've described. See if the engine is physically lifting up, implicating a broken motor mount. If you're not sure, compare engine movement in reverse vs forward.
    – MTA
    Oct 30, 2023 at 12:35
  • Thanks so much for your comments! Sorry for the late reply. I'll try to do what MTA suggested this evening after work.
    – Joseph H
    Nov 2, 2023 at 21:24
  • So I got home and was about to try the maneuver. Unfortunately, there are two reasons preventing that: 1. I can't see the engine from the driver's seat due to it's low position in the car; 2. Given the extreme shocks caused by the problem, I would feel uncomfortable performing the maneuver with the hood propped up. However, I will look into diagnosing the motor mounts some other way. Any ideas for that would be appreciated. Thanks again for the suggestions.
    – Joseph H
    Nov 3, 2023 at 1:32

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