One problem related to transmission gear slipping has been reported for the 1999 Plymouth Grand Voyager. The most recently reported issues are listed below.
Was driving on highway and transmission slipped from drive into lower gear. Was unable to get back into drive. Took vehicle to dealer and they relplaced the sensor that tells the trasmission what gear to be in. On 9/27/2000, while driving on the highway at approximately 60mph, the vehicle began to make a rattling noise. I took it to the dealer and they said there is now a mechanical problem with the transmission. The exact problem has not been diagnosed because I refuse to pay the $315 they are charging to diagnose the problem.