Any information will be greatly appreciated. I have two rx300s. Trying to use transmission from 99 for my 2000 - mechanic says won't match up to mount. Is there not a way to "convert" it to work? Both had transmission issues - 99 was rebuilt - 2000 complete transmission failure..... Attempting to salvage later year model to use.

 

Please add details about AWD/FWD for each model.
From what I know AWD/FWD swap (or reverse) can not be done. Given enough manufacturing resources, one can adapt, but nothing straightforward exists.

I would also respectfully add that you need to trust the mechanic, If you have good reasons not to trust, then get another mechanic. [hopefully who does not simply 'yes'].
Salim