2000 bravada won't go into drive unless I rev it to 3 or 4 grand

This will require *hands-on* testing by qualified personnel using a professional quality scanner .. There are a few possibilities but I feel it's not helpful to simply post a list of these possibilities as the final repair procedure is normally beyond the average DIYer's capability. AAMCO Transmissions offers free diagnosis with no obligation .. Another option is local auto repair facility. A professional quality scanner is an amazing diagnostic tool that can show the technician exactly what is happening via the transmission control module - while viewing the on screen live transmission data. There is absolutely no need to try guessing at any automotive related problems - especially when there is technology available to positively identify and determine the source.

Delayed engagement can be caused by low trans fluid. Start by checking your trans fluid level with the engine running and in park. If its low you probably have a leak. If you need help from a pro here is a link to find a shop near you. https://repairpal.com/repair-shops Alex