Nissan Repair: 1986 300ZX Turbo Transmission issue, manifold vacuum, vacuum valve

Question
WHen the vehicle comes up to temperature, the transmission will not shift into top gear.
Shifts fine through the other gears.
Once it cools off, starts shifting fine again.

Answer
Barry,

I would replace the computer temperature sensor that feeds temperature data to the computer.  Otherwise, I would be looking at the overdrive sensor that allows the transmission to shift into forth gear as well as locking up the torque converter.  It is a intake manifold vacuum valve.