Q: Transmission does not up shift on 1999 Plymouth Grand Voyager

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The transmission does not up shift and the speedometer is inop.
(2) Answers
Have the transmission checked out. There is a speed sensor that is used for the transmission and the speedometer that might have a problem. There should be codes stored in the transmission control module.
Same thing happened to me on my 1999 Plymouth Voyager. There are two "speed sensors" plugged into your transmission like spark plugs. One is the inlet and the other is the outlet. Good news- They cost only about 20 bucks a piece at the auto part store. The sensors can be a pain to find. Mine were on the driver side of the transmission in the front a few inches behind the radiator. You will need a 1 inch deep socket to get them in. Although the outlet sensor causes the problem you are having, replace them both as long as you are in there. You don't have much room to work on them- so take your time and keep yor cool...