So it was fluid after all...! Glad you got it figured out...Hope it stays working! GL!

 

As a normal rule, these Lexus auto trannies are almost bullet proof. It is important to change out the fluid at the proper intervals though. Also...don't forget your differential fluid...got to do that to!! Do a power steering flush as well while you are at it....and brakes....and coolant....and oil....need I say more?