A friend of mine owns a 98 2500 with an automatic. He's been having a problem for some time that I was hoping some folks here might be able to shed some light on. I'll do my best to describe it. Essentially, when driving at pretty much any highway speed, after anywhere from 5 to 15 minutes the truck will suddenly yield very little power, similar to a "limp home" mode in many newer cars. It will downshift or upshift fairly normally (if there is enough power to require an upshift) and it shows no signs of engine failure or critical conditions. Oddly, by simply shifting into Neutral and letting off the throttle just long enough to drop the rpm's to 1000 or so, and then shifting back into Drive, normal performance is restored.

We're pretty much baffled by this, but then neither of us knows a thing about these transmissions. If anyone can help it would be greatly appreciated. We can provide OBDII reads too, if they're helpful.

 

I would check your fuel pressure. Sounds similar to the problems I was having with my 01 and it was my lift pump which took out my VP44.

 

Also clean bat terminals. These tranny's hate corroded terminals.