My truck will shift through all gears fine until i get on the highway and it shift down into 3rd to pass. After it shifts down it won't go back to overdrive at all not even if i stop. I have to turn the truck off to reset it. I have 36x14.5 inch tires on my 93 2500 sierra and installed a jet-accu speed chip to calibrate the speedometer and shifting. It help a little with the shifting. I feel like the rpms are higher than they should be even when it is in OD. Other gmc's rpm's are about 2000 at 65mph and mine is at 2500. Do you think it is just my tires or my transmission?
Aug 23, 2010 at 4:10 PM
