Here's a problem I hope I can get some help with.
1998 Chevy K2500 350, 4L80-E, 4.10 gears. I have this issue when it's
warmer outside, about 50? or warmer and/or when I've gotten the truck good
and warm, i.e. pulling my trailer, extended runs at 75+ mph. When I come to
a stop, with the tranny still in gear, the revs will jump up and down 2 to
300 rpm's, causing the truck to lurch. If I put it in neutral, the surging
stops. The hotter the day, or the truck, the longer the surging lasts and
the higher the revs. I don't get a check engine light, don't see anything
abnormal on the gauges, i.e. temperature isn't higher than normal. And very
occasionally, I will get a hard 1-2 shift or 2-3 shift, like someone hits
the underside with a sledge hammer. No tow-haul mode in this truck.
This is what I've done so far, changed fuel filter, plugs, wires,
distributor cap, rotor, changed trans fluid. Cleaned the IAC valve, it's
hole in the throttle body, and did an cleaned the carbon off the throttle
body the best I could without removing it. Pushed together all the
connectors I could see.
Dealer was of no help at all. They didn't know what to do without it
tripping a code.
Any and all help in this matter would be great. Would really like to get
this while it's still cold outside.