Transmission Drops To 1St Gear When In Overdrive

[Lexilover64]

More shifting issues on the RX300.

While driving in overdrive about 6-10 miles, engine completely warmed-up, no cel, no codes, Engine goes into 1st gear, high rpm's.

I can shift into manual 2nd. Transmission has been tested by reputable shop. No tranny problem.

I have tested all of the VSV's, Vapor canister, Inspected all hoses except above the gas tank.

Replaced the gas cap twice. No change.

It runs perfect until it kicks out of gear. after it has done this, when I shift into reverse it is very hard and abrupt.

Also, when removing the gas cap I don't hear the air rushing into the tank.

The hose from the air filter is connected on both ends.

HELP!

I am tired of throwing parts at it.