Did you solve this problem? It most probably is the computer ECU. The early 2000 RAV4 automatics had a problem with the ECU that controls transmission. The ECU used non-lead solder as an environmental thing, but it is not as good in situations with vibration. There is a guy in Melbourne who will send you a rebuilt ECU and instructions and you send back your ECU after you fix it. ECUMAN.com.au. I did it and it worked fine.