1989 Dodge Grand Caravan Overdrive Transmission

I have a 1989 Dodge Grand Caravan with the 3.L - 6 Cylinder engine and overdrive automatic transmission.
About a year ago (October 2004) the transmission started shifting into low with a thump (akin to having a bowling ball rolling in the bed of a pickup and hitting the front of the box when you slow down). This was only at speeds of 35 mph when slowing down for a stop. I drove home (Iowa to Montana--about 1200 miles). This problem continued intermittently and then I started getting a sound like an old wringer washer occasionally. Was told by my mechanic that I needed a new transmission. This was the end of March 2005 .The transmission was rebuilt.
Everything seemed to be okay until I took a trip from Montana to Las Vegas (560 miles the first day and 450 miles the second day). Upon my arrival, I pulled into a parking lot and backed up to get into a parking space and when I went to pull forward to go into the parking space, I had no forward gears--no low, no drive, no limp gear, only reverse. I called my mechanic and he said this was a common happening with that transmission and to shut the engine off and wait a few minutes and it should work okay--which I did and it did but after this it is back to shifting into low with a bang as described above.
Upon my arrival home the mechanic checked it out and could find nothing wrong. I finally figured out that the no forward gears only happened when the van has been driven over 100 miles. Code 62 started showing up and this September after driving from Montana to Iowa a speed sensor (piece on the firewall and a piece on the side of the transmission). Codes were reset and every thing seems to be fine.
Then I found out that after driving 20 miles or so: 1. if you shut the van off and then restart it the transmission will not shift out of low until you sat with the van off for anywhere from 15 minutes to overnight. 2. If you put the van into reverse, backed up and tried to go forward--no forward gears until you sat for a half hour or so. I learned not to shut off this van until I was at my nights destination.
Back home to Montana and into the mechanic it goes, another speed sensor (code 15) was replaced. I picked the car up, backed out of the lot, drove 8 miles across town, backed up to the delivery door, shut the engine off, loaded the van, all this time barely noticing the shifting, then I drove home (15 miles) and pulled into my driveway. Van had been starting to shift a little rough while in town but the last 10 of the miles were interstate driving.
After an hour, the van was started and I backed out of the driveway and it would not shift out of low. Back home called mechanic. He arrived with wrecker and backed van out of driveway and he had no forward gears. Pulled van onto wrecker bed and now the transmission is in pieces in his shop and he can’t find a thing wrong with it!
Help! Is this van possessed?

There was probably not much wrong with the trans the first time. It sounds like a computer problem. There has been several rewrites of the transmission computer code over the years. I take it that the mechanic you speak of is a private mechanic and has never loaded the latest flash update to your trans controller. The trans controller may actually have some defect, that can probably be determined by the dealer. There is an extensive procedure that has to be done after a rebuild to "condition" the trans controller, otherwise the rebuilt transmission can be damaged. The procedure involves lifting the drive wheels of the ground and doing 40 to 80 repetitions of 0-30-0 and 0-60-0 and then some actuall drive cycles 0-30-0, 0-60-0. The procedure allows the computer to learn about the new transmission. Skipping this step can lead to premature if not immediate failure. If the mechanic knows nothing of the conditioning procedure, you have the wrong mechanic.

While I may agree that it sounds as if the problem may never have been the tranmission to begin with, and your 'mechanic' has misdiagnosed the entire problem, I'm not so sure about that "break in" procedure. Yes, it is very possible that your van's issue may be the ECM (computer) or the Transmission module, and I'd bet on the ECM not the Tran module. I would NEVER recommend letting the wheels turn while they are off the ground. Same goes for getting stuck in mud or snow. Letting those wheels spin freely will overheat that transmission faster then anything I know. Overheating the transaxle is right up there on the list of what gives these things the bad reputaion - along with incorrect fluid used and misdiagnosis.

If you change the ECM simply driving your normal routine will 'train' the module. No other effort is required to the best of my knowledge.

Yes, 95% of all 1989 Chrysler 604 trannys are possessed. :) In 1990 they made a lot of improvements that ridded the trans of most of the problems. But in 89, the first year for the 604, there were lots. I can't believe a 1989 604 is still working at all. Sorry and good luck

andy

Heat is not a concern with lifting the wheels to do the break in procedure, because there is no resistance, there is no heat build up. It would be different if you were stuck in the mud and spinning that much, the resistance would heat up the transfluid and the trans would be ruined.

Heat is not a concern with lifting the wheels to do the break in procedure, because there is no resistance, there is no heat build up. It would be different if you were stuck in the mud and spinning that much, the resistance would heat up the transfluid and the trans would be ruined.

But if the wheel is spinning in the mud or snow (ie no traction) wouldn't that also mean there is no resistance, as in this 'break in' procedure? Just wondering.....

Also, I've replaced a few ECM's that others have been told they needed programming or break-in procedures and I have yet to see one that needed it. Maybe I'm missing something......?

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I saw the procedure in a repair manual a long time ago. I can't find a hit for it on the Internet, so maybe the procedure is outdated because of software or other improvements to the trans controller. I remember that the manual said it was very important for the rebuider to do it to ensure the longetivity of the rebuilt trans. Since I can't verify, nevermind.