In overdrive, when I press the gas pedal and it tries to downshift, it feels like it rapidly shifts between overdrive and second gear very quickly and abruptly, as if it can't make up its mind what gear it wants to shift into.

When I take the overdrive off, and mash the gas pedal, it's completely fine.

Also drives perfect at part throttle. Shifts feel completely normal @ part throttle.

It has 13K miles on it, and no problems before. I changed the tranny fluid 3K miles ago to compatible spec'd synthetic, along with a new filter. Tranny has no valve body, no line valve mod, no increased shift pressures.

Anybody experience, or hear of this before?

 

When you changed to synthetic did you drain the torque converter? Gregg Evans built my tranny and told me that if I went with a diffrent tranny fluid then he puts in to make sure that the torque converter is fulley drained. He said that the stock tranny fluid dose not mix with the synt.

Hope this helps,

Peace,

Suavy

 

I disconnected the return line and started the truck pumping fluid out. I stopped after close to 8 qts.

 

ttt

 

I restored the factory tune back into the computer tonight and I did not act up. I will drive it more tomorrow with the stock tune just to reassure myself that the problem is fixed. Then, I will load a different (but similar parameters) tune into my truck and try it. It's almost as if somehow my tune that was in the truck somehow got corrupt. I don't know how that is possible since this is the same tune since the beginning of this year, and this has never happened before.

 

Today, I loaded my performance tune back in, the one that was from January dyno session, and the tranny has not acted up whatsoever. I'll have to conclude that somehow, just through useage, the program in my truck's ECM became corrupt.