I replaced the output sensor. The P0720 code cleared and the bucking stopped. But the speedometer is still jumping around when I'm at a stop.

 

So it jumps only when stopped in D or 3, but not in P? And both the speedo and odo are ok as soon as you start moving?

 

Exactly. As soon as I start moving, the speedometer reads fine.

 

Well, that's odd because the new sensor sounds like it's working ok and sending a good signal. You might just want to check the sensor connector for any gunk or dirt, and make sure the wires look good. But that stuff isn't likely to be a problem. Maybe disconnect the battery and see if the BCM does a relearn or reset and makes that jumping go away.

 

Well, the gears started jumping again on the way to work this morning.

 

Having the problem come back like that makes it seem even more like a bad/exposed wire or bad connector. Were you able to check the wiring and connector to this sensor, going as far as you can along the wire path? Of course it could be other things - a bad part out of the box, PCM problem, or even the famous bad battery (which can cause just about any problem in our vans). My money though is on the wiring/connector.