I just bought a 2007 Chevy Silverado LS 4.8 v8 and the other day I was driving on the interstate and had to pass someone (and was a little curious to see how fast it would go.) when my truck hit 100 mph the rpms dropped and it felt like it shifted into another gear.was it the over drive?

 

Your truck only has 4 gears. 4th would be your "overdrive". You may have been down in third as you accelerated then it shifted into 4th or your torque converter may have locked up causing your RPMs to drop making It feel like another shift.

 

Electronic speed governor. Kills the fuel.

Get a tune. It can be raised.

Have had my Burb at a GPS-verified 107 MPH out West.

 

warp drive??