Erratic shifting at 35 mph to 40 and also at 45 mph to 50

[SMalafy]

I bought a newer truck about 3 weeks ago (2001) and after I had bought it I noticed when I would go at certain speeds of between 35 to 40 and 45 to 50 the transmission could not make up its mind which gear it wanted to be in. If I do not stay in those speed ranges the transmission shifts fine. My fluid level is OK. My old retired 95 had this problem with 3rd and overdrive but there was a lock out button to stop that.
I know that this has happened to others so can someone point me in the right direction. Thanks

 

[john reitz]

I have had and continue to have the very same problem. Here is what i have discovered. Clean each and every ground strap (I think there are six) between the body and engine so that there is shiny metal. Replace the bolts or nuts with new. Torque to spec. Coat the cleaned junctions with dielectric grease or clear nail polish. Also remove and totally clean to shiny all battery cables at each every end. What is occurring is a minuscule voltage drop that feeds an incorrect reading to the APPS and PCM. Because i am in a very humid mid-Atlantic state and we use salt every winter, I have to periodically repeat the process. Once your establish good ground, you should notice a smooth shift. Good Luck.

 

[SMalafy]

I have had and continue to have the very same problem. Here is what i have discovered. Clean each and every ground strap (I think there are six) between the body and engine so that there is shiny metal. Replace the bolts or nuts with new. Torque to spec. Coat the cleaned junctions with dielectric grease or clear nail polish. Also remove and totally clean to shiny all battery cables at each every end. What is occurring is a minuscule voltage drop that feeds an incorrect reading to the APPS and PCM. Because i am in a very humid mid-Atlantic state and we use salt every winter, I have to periodically repeat the process. Once your establish good ground, you should notice a smooth shift. Good Luck.

I found a solution by rerouting the ground wire that goes around the back of the alternator and then I reprogrammed the throttle position sensor and have not had the problem any more. I found the link somewhere in the forums but I forgot where. Thanks for the reply anyway.