How do I know if I need a trans rebuild. The truck shifts fine through all the gears (auto) but wont drop down into OD. I have replaced gov pressure switch and solenoid, TPS and had bands adjusted. So far I'm sitting at like $3500 CAD less in the wallet. I plan on adding some HP(max 4-500) in the near future...should I just say F it and go for the upgraded rebuild? THX!!