Okay, maybe I didn't phrase that very well. Everyone knows how the 3.0 auto trans will not shift into overdrive until the engine is up to operating temp. That wasn't such a bid deal until

1. Engine cooling system gremlins made it necessary for me to run without a thermostat,
https://www.yotatech.com/forums/f116...-kaput-148212/ (long thread)
and
2. Morning temperatures got a lot colder recently. This morning I drove 23 miles to work with no overdrive.

Now I'm wondering if there is a relay or something that controls this, and if I can remove or override it.

 

my truck did the same. i got 11 mpg with no overdrive so im in the process of putting a manual in.

 

There is a blue sender on the coolant bypass manifold at the rear of the intake that controls the OD. I assume that you could just jumper it to ground (I think it is a one wire affair)to bypass, but I may be wrong. Maybe someone more in the know will chime in with consequences that I have not thought of.

 

Has anyone here ever done this? Doing 45-50 miles per hour with the engine turning 3000+ rpms is getting old. I can't imagine why Toyota set it up this way in the first place.