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sv1cec 06-15-2011 04:28 AM

Gearbox won't upshift above 5000 RPMs '02 Overland
Hey guys, I have a strange problem with my 2002 WJ Overland. More precisely:

The gearbox refuses to upshift, if RPMs are above 5,000. In other words, starting from a traffic light with the accelerator to the floor, the engine goes up to 5,000-5,500 RPMs and it stays in 1st without upshifting. Same thing if you do a kickdown to pass another car, if you keep your foot down, RPMs go up but the gearbox doesn't upshift, unless you let off a bit.

Below 5000 RPMs (or thereabout) the car behaves fine, upshifting and downshifting correctly.

The car diagnostics do not show any problem.

So far, we have changed the Throttle Position sensor and the Pressure sensor on the gearbox, with no results. I live in Athens, Greece and my mechanic and me are at a loss about the cause of this problem. A Chrysler dealer mechanic in US, who I consulted through a friend, is also at a loss, he says they have never heard of this problem before.

Any ideas would be greatly appreciated.

Frango100 06-15-2011 06:28 AM

Re: Gearbox won't upshift above 5000 RPMs '02 Overland
Welcome to the garage.
Did the car sit for some time with a dead or disconnected battery? I heard of same problem and in that case the battery was disconnected for some days due to maintenance. The TCM will loose its memory and has to relearn the shift points. A TCM flash was necessary in this case.

sv1cec 06-15-2011 06:35 AM

Re: Gearbox won't upshift above 5000 RPMs '02 Overland
Thanks for the welcome.

Well, I do not think it has been sitting there, for any significant time. But we have tried the "re-learning" process, but I am not sure. My mechanics computer is not the same as the one Chrysler is using, but we have found someone who has the real-thing, so we plan to do the whole procedure next week. We'll see if that will correct the issue.

Thanks for your idea, appreciated.

mandio23 06-15-2011 03:37 PM

Re: Gearbox won't upshift above 5000 RPMs '02 Overland
That happened to me a few months ago, it drive me crazy! It was a pain on the behind to pinpoint. Make sure you transmission pan is not hit or bent. Mine was hit right below the oil filter, so when it went above 5,000 rmp it couldn’t suck enough oil and it would shift.

sv1cec 06-15-2011 05:46 PM

Re: Gearbox won't upshift above 5000 RPMs '02 Overland
So if there is not enough oil in the box, that can be a symptom? I am sure there is enough oil in it, but maybe there is some dirt in the system? Shall I ask my mechanic to empty the gearbox and refill it with oil? I do not think there is any hit on my pan, the Jeep hasn't been off-road almost at all, so I can't think how the pan could get hit. But I'll definitely check it out.

Frango100 06-15-2011 06:00 PM

Re: Gearbox won't upshift above 5000 RPMs '02 Overland
When you don't know the service history of the jeep, its a good idea to change the fluid and filters to start with. (also all other fluids/oils and filters would be recommended, just to start from 0)
Never heard about this specific problem caused by filters/fluid, but sometimes the tranny starts behaving strange when the filters are getting too dirty.

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