Drove to austin today on the way back the truck felt "heavy" it would downshift with the lightest press of the accelerator pedal. And needed to drop to 2nd to move the truck. Also on a hill by the house it was shuddering at about 20 mph under slight load. Its a 4.8 with tsp 220 n 3200 circle d stall stock tranny. It drove fine on the way up there n trans temps never passed 170. Is it time to upgrade or?

 

Did you check the fluid level and condition??? Have you ever had the transmission filter changed???