My wife's '04 Expy has what I think is a shifting issue. Steady throttle always around 40 mph. It is almost like the trans is confused what gear to be in. The truck doesn't shudder violently, it is almost like the motor has a misfire. You can repeat it almost every time, same mph same engine speed.

She had the tranny pump seal replaced about two years ago and they also put in a brand new TC. I assume they replaced the filters and fluid.

Truck has 130,000 miles.

Any ideas?

 

I'd say it is a miss fire and not related to the tranny. The pending codes can be read and tell you for sure, but that is a very common first thought you have had about the tranny when in fact it is a misfire. Have you done COPs and plugs?

 

I suggest that you change the fluid and filter in the trans as it would be due by now in any case. Check the trans pan for debris and/or metal, clean the magnet and pan and reinstall it using the original gasket. Drive it for a few days to see if the problem persists. If not, all is good. While cleaning the pan look carefully for metal flakes before you wash it out, if there is a lot you are due for a rebuild or replacement. If all is good in the trans start looking for a problem with the ignition or injectors. Getting the codes read by a shop or parts store will be a good guide.

 

i had very similar symptoms and it turned out to be a misfire actually, thought it was the tranny. i changed all the plugs and coil packs and it was like new!!