Adjusted TV cable. Fluid level is proper.
350 in a suburban, with 35" tires.
Stock rear-end gears.

On the freeway when I'm cruising, if I go to WOT it will pull and pull, but when the speedo reads ~75mph, (actually more like 90 since it hasn't been calibrated with the larger tires) the motor sounds like it's spinning past 5-6K and it won't shift up to the next gear. I have to let off for it to shift. But when I am trying to go fast uphill, I can't get past a certain speed (speedo indicated 60-64mph) Any ideas?

THANKS!

 

What gear will it not shift into? If it will not shift out of first, it is likely a stripped governer gear.

 

If it won't make the 2-3 shift at WOT, then this is common on the 700R4. A Corvette servo & larger boost valves at a minimum will help this problem, if the 3-4 clutches are still in good shape. What rear end gear ratio are you running now?

 

does the engine have a fan clutch?

if so the fan cluct can lockup and make the engine sound as if its reved to high while driving.

 

Ya, 2-3 shift. I forgot about the need for a larger servo.
2.73 rear gears.
I'll check the fan clutch....

 

I would definitely check the transmission pressures. I had the same problem and did change everything to high performance except the pump. Nothing could help really.
Finally I changed the pump and everything was right.