At higher mileages, (125,000-150,000) the automatic transmission may not shift correctly. This can be caused by the throttle position sensor being out of adjustment or a shift solenoid needing to be replaced. Typically the transmission does not need to be completely overhauled.Google+
Car Problem Reports
Toyota Pickup Automatic Transmission May Not Shift Correctly at High Mileages
Toyota Pickup Problem
Drive Trains Affected: 2WD, 4WD
Average Mileage: 150,003 mi (114,000 mi - 186,011 mi)
Transmission will not downshift when depressing the accelerator on the highway, or when going on a slight incline at a speed higher than 30 miles per hour. I have to manually drop the transmission from D to 2 in order to accelerate when not on the Highway, and I have to disengage overdrive while on the highway. I intend on replacing the shift solenoids and installing a performance kit in the valve body to remedy the problem. If I absolutely need to, I will replace the TPS (throttle positioning sensor) and have it calibrated (although from what I understand it is a simple open circuit, closed circuit switch and not a proportional switch as the ECM, EFI, and control system is somewhat obsolete).
Visitor, 1994 Toyota Pickup, 2WD, 114,000 mi
Won't shift unless let off the pedal..