i have had problems with a bad trans temp sensor. if i says it's under x degrees it wont let the truck go into overdrive, or in your case it bounces above and below this threshold making it kick in and out....

 

ordering a dnr customs tps delete saturday, ill let you know how it works out

 

It does sound like your TPS. You can check it with a volt meter. Put a paper clip in the back of the connector (middle wire) connect the positive lead to that then the negative to the neg side of the battery. Turn the key on but do not start the truck. The at rest voltage should be .6 - 1.2. Advance the throttle linkage and the meter should move to 2.25 and 2.75. I have a new TPS for sale. I switched over to the potentiometer due to the small plastic connector that is between the fuel pump and the TPS was worn and constantly causing my TPS to go out of adjustment. I found this out after buying a new TPS. If you are interested in the TPS contact me at jeffdavies500@gmail.com

 

can someone show me where the VSS is located on the tranny??

 

Vss is on the rear of the transmission. It threads in with a pipe fitting looking ring. Look one up on rockauto and you'll see what to look for. I just bought a new one because I lost speedo and last week it had been jumping in and out of overdrive.