I was thinking this morning about how cold it was and it reminded me of a question i have always wanted to ask.
Here Goes.
My:
Ford Focus 04
Toyota Crapolla 94
F250 psd. 01
All do this. When they are cold they won't lock converter and go into OD until the temperature hits a certain degrees. You can see the temp rising and when it hits the mark on the temp gauge it will shift to OD and/or lock TC. It is predictable on all three different vehicles. I suspect to help warm things up? I am wondering what is the factor and how does it know? Heat/tranny pressure. The temp sensor? It may be a dumb question but it is something i always wondered about.

I work right next to the thruway i travel home from work. You should hear my Crapolla when i leave work if i take it up to speed before i let it warm up. Sounds like a weed wacker if i don't let it warm up before heading above 55mph.

Just curious. Thanks in advance.

 

I Always believed it was reading the temp sensor. But someone once told me that it is the tranny and when the tranny got hot it would build up more pressure. I doubt that and is why i am asking. So basically to prove it i could disconnect my temp sensor and see if it acts like that when hot?

 

You are correct the TC doesn't lock and the trans slips to build heat. So It can get to operating temp. It is really noticable at -0°F.

 

There is a temperature sensor inside the trans that sends the temp data to the PCM. The PCM decides at what temperature to allow lockup. And yes, it's to help warm up both the engine and trans.