Dodge Grand Caravan Transmission Problem

A few weeks ago, I had the following work done on my 2002 Dodge Grand Caravan: new tires, a front end alignment, brake inspection, and a transmission fliud flush and fill.
When I left the service center, I noticed a problem that had not been there before. After bringing up the speed to at least 35-40 mph and then slowing down, there was a very noticable pull/grab/minor jolt when slowing to about 25-30mph. At first, I thought it was a brake problem and assumed something went wrong during the brake inspection, but when I had the front and rear brakes done at a different shop two days later, the problem persisted.
I strongly suspect a transmission problem (4 -speed automatic). When the problem occurs right around 1000 rpm, the tach jumps about 2-3 hundred rpm. It feels more like a slip than a grab. Also, the problem only occurs in D.It will not happen when driving in 3. Up and down shifting is completely normal at all point with the exception of what I described. I assume the problem is occuring when downshifting from 4 to 3.
I took it back to the original mechanic. He confirmed that the transmission fluid was filled with fresh fluid. He took it for a test drive, confirmed the problem, but couldn't figure out a cause.
He consulted with some transmission guys who suggested clearing the computer by disconnecting the battery. I tried it a few minutes ago and it didn't work, at least not on the first test drive.
I have 109,000 miles on the van. I had the transmission flushed back at 58,000 without a problem.
What could have happened to cause this? What possible mistakes could have been made that would result in this problem?
Thanks in advance for your opinions.
Rob
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On Wed, 28 May 2008 17:44:38 -0700 (PDT), snipped-for-privacy@hotmail.com wrote:

    It's the 4-3 downshift, at 28 mph. May or may not set a fault code. My '02 has done this three times, not necessarily at fluid change time. The only remedy seems to be to flash the software in the powertrain control module.     The first time, the dealer flashed the PCM and sent me on my way. It was OK for about 15.000 miles.     By the second time it happened, I had discovered that there's a tech bulletin about this. Service Bulletin 21-004-05 details the condition and the fix. They say the front pump needs to be replaced. This was done on my van, under warranty, and it was OK for about 25,000 miles. Then one day it happened again, for no apparent reason. Out of warranty, I had the PCM flashed again by a dealer, and that "cured" it for the third time. The service manager said I should bring the car back to him "some time when he could spend some more time with it." In other words, they don't really know what causes it.     The likely remedy is to pay a dealer to update the PCM. Can't be done by most independent shops, because they don't have the files, and most aftermarket scan tools apparently don't have the capability. Seems like the last time cost me about a $70 minimum, to hook up the machine.     Damned electronic transmissions.
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wrote:

My 2002 GC ES with 3.8L now has about 103k on it. I have had the 4-3 downshift problem recurring for the entire lifetime (since about 12k miles and beyond). I did manage to get the tranny torn down twice under maintenance - replaced burnt torque converters once and some other parts the second (~ 80k). But when I picked up the van that time it went into limp home mode. Grrr... Having the dealer "flash" the PCM "cures" it. But they haven't changed the actual files they flash for a few years (see the TSB above). If you don't want to spend the ~$70 for a dealer to flash, you can disconnect the battery OVERNIGHT. The PCM should revert to it's original "learning mode". If not then go back to the dealer.
This is only hearsay and does reflect my experience - though more knowledgable folk (MaxPower etc) may have more accurate or better ideas.
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On Thu, 29 May 2008 18:06:55 +0000 (UTC), Steph

    If disconnecting the battery actually works, that would be fine with me. I haven't been so lucky, nor have a couple of other owners I know. Flashing the software seems to be the only remedy.     I'd give a lot, to have a good late 60's-early 70's hydraulically-controlled transmission available to me in a new car. The advent of electronics has been good for engine management, but utter crap for powertrain control.
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Found an interesting thread on tranny problems http://www.automotiveforums.com/t196775.html
And yeah, it hurt for me to give up my 1978 E-250 with a 460cu engine. All you needed for repairs was a large screwdriver, hammer, duct tape and some time to let the carb cool down after getting vapor locked.
Anyway search google on flashing (PCM, TCM) caravan
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I do understand your perspective about the simplicity of hydro-mechanical transmissions, but still must disagree. Electronic control is superior when properly designed because it can compensate for changes in pressure, temperature, and system response due to wear.
To cut costs manufacturers can simplify the system (automatic transaxle in this case) based upon design goals, system capabilities, and observed characteristics of production units. Changing ANY parameter from the base system (using non-OEM parts or fluids) will cause a change in performance, good or bad.
Having said all that: Did they use ONLY Chrysler approved ATF? Having problems after transmission service tends to indicate that the fluid is the problem. Putting the TCM into learn mode might help it compensate for this, but the real solution is to get the correct fluid in the transmission. It may take multiple fluid changes to get it working right, but it will get better after each one.
Maybe I'm full of crap; maybe I'm right. Don't flame me, I'm just trying to help. Good luck!
--
Gyz

Everyone thinks they know how to drive.
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On May 28, 8:44pm, snipped-for-privacy@hotmail.com wrote:

Hey Rob, I have a 2003 dodge caravan grand with 3.8 engine. I changed the tranmission fluid and filters myself. I don't mind doing things mysefl to save money. Anyway just after that I had the same issue. when I drove the van it was fine. When I was coming to a stop around 30mph the transmission would jump more like a thud. I went to an old timer that has been working on transmission for over 50 years and he hooked the van up to a computer and reset the timing because of the new fliud that was in there. The computer was changing the clutch back because of the fluid change. The computer rembered the old fluid and set it. In the manual there is a peice that says you might need to service after a fluid change. Anyway it works fine after he realigned the clutches by the handheld computer. Thanks Warren
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