Ive got a 94 4Runner with the 3.0 auto...tranny wont shift into 4th/OD unless warmed up (which takes like 10 minutes) and recently Ill be driving down the highway warm and in 4th and all of a sudden my temp. gauge goes down and the tranny gets kicked out of 4th....I checked the fluid, the coolant temp. sensors and it all checked good 
All help will be appreciated 
thermostat sticking open?
