I have a 2002 early model quad cab quad cab automatic diesel of course that has a strange shifting problem at 45 miles per hour.vehicle shifts in and out of top gear constantly between 45 and 52 m.p.h.took it back to dealer i bought it from and they changed tps 450.00 which they ate and said problem cured.well it wasn't took it to another dealer and they installed ground wires from computor to body to engine ta da cured.now 6 monthes later it started again.i took ground wiring apart and wire brushed with a dremel and re installed and now truck shifts fine.if anyone has problem like this any more advise would be helpful.

 

If you're talking about floating a few mph within that range I think it's normal. That is if you just have your foot on the pedal a little bit. If you're really trying to accelerate and it shifts down, think that's normal too. If you're trying to really accellerate and it shifts up and down a lot, then it's a problem (Torque converter/valve body?). Mine will shift up and down around 35 and again in your speed zone too if I'm light on the pedal and slow down a bit and then try to pick up a little bit. Think it's the truck/tranny trying to decide if you need power or mileage, ie... shift points. If you take it up a couple mph over that range and hold steady does it keep shifting?

 

Ground has caused this. Put the rap tin foil around the wire at alternator trick. Also, how many miles since last tranny fluid, filter change

 

please explain this trick in a way that we can understand.

 

Well, its been a long time ago now. But if you do a search you should find it. I will try to remember, but my memory isn't so great. Take aluminum foil and rap it around the alternator wire at the alternator. If i remember right it only takes 10 inches or so. Then rap that up with something, I can't remember what, probably electrical tape. Then I put plastic zip ties on the ends of that to make sure it don't come off. This is supposed to help by reducing the interference you get from the wire. Also you can put on the mystery switch to lock the torque converter. I use it when in that situation so it stays in gear without shifting back down, just gotta watch if rpms get to low to take it back off.