I just had my auto tranny replaced in my 91 v6 4runner and the truck is not shifting into overdrive and I find myself at 3800rpms trying to keep up with freeway traffic. My previous tranny had the same problem so I am afraid its going to cause my new tranny to blow also. What could be causing this? I am thinking its something electric like speed sensor maybe?

 

Is it getting to the proper running temp? If its even just a little low, the tranny will stay out of OD.

 

Ditto. When my '89 wasn't warming up all the way, the temp gauge was only a hair below normal, but it was enough to keep me out of OD. A new thermostat took care of the problem.
How long does it take your truck to get up to operating temp? Anything over 5 minutes is too long.

 

What they said.