Puzzled

I have a 2011 Tacoma 4x4 bought used with 34" Nitto Grapplers and a 6" Pro Comp lift. I have noticed that when reaching cruising speed 35 to 40mph that the rpms will shift down and loose power a little than go back up. Pedal in the same position. Could this be a gearing issue?

 

Probably gearing related, I'd go with some 4.88s. You could always take it to the dealer if it's still under power train warranty.

 

It is still under warranty but is there any exclusion due to lift kit and tires?

 

Tranny is auto