Tonight when driving back home, for the first time, at about 45 miles per hour on wide open roads, the truck was quickly upshifting and downshifting about 4 times before finally shifting to the higher gear. This happened repeatedly along my 15 mile trip. I even pulled over and shut the truck off. i've never seen this before. The engine would shift normally for the first few gears, and then when it came time for the last shift it would seem to shift, and then shift right back, and up again, and down again. If i punched the throttle it would finally stick where it was supposed to be. This was definitely not normal, and has never happened before. Can anyone shed any light on what could be going on, or why the truck suddenly did this? I checked the trans fluid in neutral when i got home and it was on the high side of the normal mark. Thanks

 

Just ran the codes and got:

P0500: Vehicle Speed Sensor Circuit

P1693: Tachometer Circuit Low Voltage

P0216: Injection Timing Control Circuit

Can anyone shed any light?

 

Sorry, but P0216 usually means your injection pump(vp44) bit the dust.

 

Sounds like it is hunting for lock-up. Do a search in it. Most likely this is electrical noise at the computer and it is telling the trans to lock-unlock. clean battery posts.
replace injection pump.!!!
Replace speed sensor on the bottom of the trans.