engine or tranny shutter in Odrive at 45mph

I have a 99 silverado 4x4 and have noticed that around 45 to 50 mph when the truck is in OD something is shuttering almost like the engine is missing. I have taken it to a tranny shop and found no problems, also it only happens after the truck has been driven a good distance over 20 miles or so. It happens when you go to give it more gas around the speed I stated. Just wondering if anyone else has had this problem any help would be appreciated. Their is not a check engine light either, I read in a SIerra forum about something similar and turned out to be MAP sensor anyone think this could be it.

When was the last time the plugs were changed???

Its only been a year ago since new plugs. Usualy if it were a plug it wouldnt matter if it were in Overdrive or not.

your timing could be off

Could be timeing if it were a 69 chevy but I dont think so in a 99 maybe something that controls the timeing.

Torque Converter? Maybe it's time to change your Tranny Oil?
The ony other thought I had is maybe your Fuel Pump is getting week?

OD unit could be going bad, tranny shops usually dont have the know how to fix trannys.....oxymoron, huh???
take it to the stealer, its worth the money on transmission codes,get them to pull the codes and diagnose, just bring it somewhere else to fix it or do it your self. the 4l60e has electronic 1st and overdrive, 2nd and 3rd are hydraulic, so most likely it is repairable.