I have about 106K on my 2002 1500 SLT. I had an overheating problem and changed out the waterpump, flushed etc. Since then I have had an odd drop in RPMs from about 2500 down to about 1200 at about 45 mph and the truck shudders until the revs pick backup to over 2000.

It seems like it is skipping a gear or two and going right into overdrive. Clicking OD off makes it rev up and smooth out, but even if I turn off OD first it will still do this at a slightly different speed.

It is throwing a P0307 code, otherwise runs very smooth when not under load (park or neutral), dropping into neutral while shuddering lets the engine rev smooth. Starts and idles smoothly.

I am suspecting a damaged gasket, because there is a tick which sounds like exhaust or vacuum leak. But could that cause these symptoms or is it most likely transmission? The fact that it smooths right out when taken out of gear makes that seem likely to me.

Thanks for any input -

 

Sounds like it wants to get up into high gear sooner than maybe it should. I'll be interested in seeing what others say about this. I have similar concerns, though mine is not skipping gears. It just wants to get in the taller gears too soon for my liking.