Bypassing the OD
 

Were is the sensor for the overdrive at the coolant? And why can't I just ground or run positive to the sensor, so the OD kick in even if the engine isn't warm?

I'm sure it just uses the regular coolant temp sensor, and then the ECU tells the tranny not to shift into OD. Bypassing that sensor would create MANY other problems.

How big a problem can this be for you in hotlanta?

If the engine is taking a long time to heat up, there's probably an issue with the cooling system that needs to be addressed first.

Have you checked the coolant sensor? They are relatively cheap and easy to replace, and I think the coolant only has to be like 60*F to allow it to shift into OD. My truck did the same thing, checked and replaced the coolant temp sensor and still had the same problem. Turns out I had leaking capacitors in my ECU (which is fairly common in 15-20yr old vehicles and no way around it.) I sent it off to a company in FL, they fixed it for $180 IIRCC and shipped it back with an 18 month warrenty. Trucks been running great since then. BTW I had a diesel ECU, so looking for another one wasn't really possible and besides, another old one would probably be leaking soon too.

We had 3" of snow last weekend, I know it's not normal but is does get cold here. Lol.
Were is the Coolant temp sensor that sends the signal to the tranny at?

yes we did have 3-4" of snow here last week along with vary cold temps during the past weeks also including today, my 4runner didn't want to shift into OD until the temp gauge got almost half way to center.during the really cold times..and that is with a new coolant temp sensor, rad and water pump......so I'm thinking the sensor may not be the problem,but the cold weather is