The truck runs fine except when you get up to 50 and the overdrive has kicked in. It starts this 'lurching' which to best describe it feels like your going through small pot holes yet your on a smooth highway.
I changed out the tranny filter and flushed it out with 18 quarts of Mercon V through the cooler line. But it still does it.
I reflashed the computer back to stock and it still did it, so I reflashed to the tow program and then up to the enhanced stock setting and it still does it there too.
I have 40K on the truck ('03) and I have this sneaking suspesion it's the torgue convertor going out.
When I changed out the fluid there were no shavings in the pan just the black crud that appeared to be the same amount as before.
Thank God I have 5 year 100K on the truck.
I'll flash it back to stock and take the 18's off and put the stock skate wheels back on and take it in. I figured I'd ask in case some one knew something I should.
Thanks

 

I have the same problem with my truck, except mine does the "lurch" at 40 mph. I too had the tranny filter/fluid changed which did not help. I'm out of ideas as to what the problem could be.

 

Well I went out and changed the fuel filter tonight. Man was there some crud there. I will fill with injecter cleaner and mid grade tommorrow and see where it goes from there.