Something internal with the trans. Ive had other cars where it pops out of 5th.

Right now there is a v6 trans and transfer on cincy craigslist for $250.

Or if you can, rebuild it

http://www.4x4wire.com/toyota/tech/r151f/


88 4R, 350 V8, R150 5 speed Sold <...uot; />
97 4R, stock, daily driver
98 Sienna, kid and dog hauler, wife's ride