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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 2008Strange 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. 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 > 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. An ATF flush can be a real crap shoot. It can push a questionable transmission over the edge. On the other hand, I've always flushed the ATF after buying a used car and never had a problem, even after 15 years on the original fluid. How many miles on the Caravan? How often is the ATF flushed? Was the correct fluid used to fill it up? Have you checked the fluid level? You might be able to fix this with a bottle of automatic transmission "medic"... It expands the seals so might help improve the shifts. >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 [quoted text clipped - 19 lines] >transmission fluid was filled with fresh fluid. He took it for a test >drive, confirmed the problem, but couldn't figure out a cause. The thing is, when you do a full transmission flush on an old transmission that has not been well maintained, you wind up moving a lot of gunk around. And sometimes you move gunk from a place where it wasn't doing any harm to a place where it does harm. The automatic transmission is controlled by all kinds of hydraulic stuff.. there are plenty of valves and modulators and fiddly things with small orifaces to get clogged up. >What could have happened to cause this? What possible mistakes could >have been made that would result in this problem? Was this the first time you ever flushed it? Had you ever changed the fluid before? How many miles are on it? Did they change the filter when they did the flush? I would think a 2002 transmission would not be so clogged up, but it might be. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > 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. Fresh fluid? It better have been fresh ATF +4 fluid. Fresh Dexron or Mercon won't cut it. > What could have happened to cause this? What possible mistakes could > have been made that would result in this problem? Using the wrong type of transmission fluid would be my first guess. >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 [quoted text clipped - 26 lines] > >Rob My first bet would be incorrect fluid in the trans. Mopars and some others are fairly picky about the fluid. IIRC, your Caravan has a specific fluid to use. Anything else and it is not going to be happy. Note: some shops use only one or two different fluids when flushing to reduce inventory. i.e: they pretty much all get the same stuff which can lead to problems. If that is the case, your trans may return to proper operation with a complete service withe the correct materials. Lugnut >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 [quoted text clipped - 15 lines] >I described. I assume the problem is occuring when downshifting from 4 >to 3. 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. On May 27, 10:55 pm, td...@hotmail.com wrote: > 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 [quoted text clipped - 26 lines] > > Rob Sounds like the converter lock-up clutch could be failing to disengage at the proper speed. So you go 40, you get into top gear, you slow down, at about 1000 rpm you feel this thunk, and the tach goes up 200-300 rpm? It could also be the trans failing to downshift from 4 to 3. Or, the trans is downshifting 4-3 without disengaging the lockup clutch. One fixall to try is to disconnect the battery, then turn the key on. I'd like to say just a short while is sufficient, but either the ECU or TCU in my subaru refused to 'forget' until I pulled the battery for several hours. Dave |
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