What would cause a automatic transmission in a 2000 Toyota tacoma not to go into overdrive 2 transmissions had been put in and both do the same thing thanx?

If TWO transmissions are having the same problem, then you could possible have an electrical problem. My suggestion is to have a shop hook your truck up to a tranex2000 or something comparable. This eliminates the computer to see if the computer is causeing the problem. From there you move on to possible faulty wireing or solenoids.. Macs Transmissions (Houston, TX) 281-394-4951 Macstransmissions@gmail.com