I have a 99 dodge with a replacment jasper tranny and when you drive down the road it goes to high gear then it will kick out then go right back in over and over what could cause this...? im stumpped Could this be caused by a bad thermostat? :

 

It's probably the converter unlocking then relocking.
This is a battery ground issue usually. CLEAN them.

 

I read on another message board that the ground cable that goes over the alternator could be catching current from the alternator makeing it lock and un lock could this be the propblem?

 

The good news is your tranny is fine, the bad news is it will take you a couple of hours of work to fix it, but it's a cheap fix.

Clean ALL the ground wires on the passenger side of the vehicle. Battery terminals, fender grounds, alternator grounds, ECM grounds. There are two gray quick connectors coming from the battery to the alternator, and from the fender to the battery. Cut them out and solder them togeather using a good electical connector. The gray connectors get corroded and send electrical "noise" to the ECM on the firewall (behind the aircleaner) telling the tranny to down shift.

 

Yep. Loose the gray quick connector and you'll fix 1/2 the problem.

Good luck.

 

Thanks im gonna try that and see if that works.

 

Mine was doing this and I just had a loose battery cable. THat is what I would try first since it is the easiest fix.

 

Also it wouldn't hurt to reset the APPS. (unhook batteries for 5min, hook them back up, turn key to on position but not start the truck, press accellerator pedal to the floor slowly ten back, turn kuy off and you are set.)

another thing to try is an APPS recalibration. that is what I had to do when I had a similar problem. https://www.dieseltruckresource.com/...ght=APPS+RESET