2003 Grand Caravan transmission slipping

Hello everyone. I have a 2003 dodge grand caravan with about 111,000 miles on it. Overall it has been a reliable car. In the past month we had to replace the ECM because the computer died on the car. Now, very intermittently, while driving at about 60 mph the car will suddenly drop to 40 mph then shoot right back to where it was at 60. This only happens for about a second and then its fine.

Its quite startling but it has only happened to us 3 times in the past two weeks, so its very hard to replicate. There are no engine codes and it seems like the tachometer does not change during this sudden drop, although to be honest I wasn’t paying that close attention to it when it happened.

Does anyone have any experience in this problem and could it be related to the recent ECM replacement? The dealer “reprogrammed” the computer so I’m assuming all parts electrically have been checked. Thanks in advance for any help you all can offer me.

Dropping from 60 to 40 mph and then back up to 60 all within a second is quite a bit of decceleration/acceleration. Are you being thrown hard forward and backward? Are you saying that the speedometer jumps down to 40 mph and then back up to 60 within a second?

Hope to help.

Another forum to try is allpar.com. It is all about Chrysler Corp. vehicles, and there is a discussion board specific to minivans and Pacifica vehicles.

Automatic transmission?

Yes sorry, its an automatic transmission and after some further research I don’t think the transmission is slipping because its we are coasting already in gear. I don’t believe that the car is decelerating, but the speedometer drops to 40 and you feel a sudden acceleration then it goes back to 60 and everything is fine. I am really wondering if its something electrical. Any help would be appreciated.

The van may have a problem with the Vehicle Speed Sensor (also known as the output speed sensor) or it’s wiring. The Transmission Control Module probably would not set a Diagnostic Trouble Code in this situation unless the VSS signel were to disappear completely.

Be attentive and glance at the tach gauge to see if the engine RPM is taking off and dropping again when this happens as that would indicate transmission is down shifting or ‘neutraling’.

Hope this helps.