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As the title mentions, I have a 2003 Dodge Grand Caravan, and my transmission sometimes downshifts forcefully with a clunk when I let off the gas. It will do this no matter what gear I'm in (except 1st of course), and depending on speed and gear, it will jolt me forward in my seat. If I put the slightest pressure on the gas pedal, it will up shift into the proper gear.

I've been driving back and forth between FL and MA (a distance of about 1,300 miles [~2100 km]) a couple times per year, and this is what brings on the issue, which will persist for a week or two after the trip. Additionally, it seems to be related to the speed I travel on the trip between FL and MA: If I go slower, it either won't come up or if it does, it will last a shorter amount of time (I.E. a few days rather than a week or two).

If I keep a slight pressure on the gas pedal and brake with my left foot, it does not do the hard downshift.

I found this post, which is similar, except my speedometer doesn't fluctuate, I don't have cruise control, and it happens in all gears, not just second to first.

Does anyone know what is causing this, and can you please tell me all I need to do is tighten a bolt (an easy to access bolt)?

Edit:

@JPhi1619, it has about 121,000 miles (~194,730 km) on it, and I changed the fluid/filter at, if I recall, around 70,000 miles (~110,000 km), right when the owner's manual recommends replacing trainy fluid.

@Rana C'mon man... no bad news please :P

  • How many miles are on the car, and when is the last time you had the transmission serviced/flushed? – JPhi1618 Oct 15 '15 at 14:43
  • Sounds like your transmission needs rebuilding. I would change the fluid and add 1qt of Lucas transmission additive to see if helps. If that does not fix it, you might have to have the transmission rebuilt. Which is going to cost you a lot. Might want to consider junking the car. – rana Oct 15 '15 at 16:01
  • Could this problem be with motor/transmission mounts being shot? – DucatiKiller Jan 4 '16 at 23:55
  • @DucatiKiller. I doubt it, I've babied this thing, no rust problems, nothing's happened that would lurch drive-train around/break them from mounts. – user1763357 Jan 6 '16 at 1:27
  • The mounts all have rubber in them. The rubber wears out, rust is irrelevant to the situation. When you put a vehicle in gear with worn out motor/transmission mounts it will make a big clunk sound because the rubber is degraded. – DucatiKiller Jan 6 '16 at 1:32
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One possibility is the combination of a broken engine/transmission mount, and worn or loose shift linkages. Excessive movement of the engine/transaxle causes a downshift as if it came from the control.

Do the engine mount test. Park in a safe spot with front/rear clearance, and raise the hood. Put the parking brake on hard, and stand on the brakes. Then rev the engine in short bursts in Park, Reverse and Drive. Have an observer with a strong light monitor each mount for each P/R/D rev test. Excessive movement at any mount point means you need a new mount. Sometimes it is scary obvious when this is the problem.

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