Torque convertors lock up when motor reaches a certain temp

[junkyardjeff]

The E4OD does that in my 95 f150 and I am wondering why the motor has to warm up a little,before the convertor locks up,would it do some damage if it would do it cold.

[Charlie Chops 1940]

There is a little known review board within the auto manufacturers that governs the number of sensors used for drive line management. It determins how many are required based on the price of the vehicle, how many hidden spots they can go in,  how many drive ability issues a failure will induce, and finally the always high cost of the is the inverse of the quality.

Nah....I don't know.

[junkyardjeff]

I think the GM trans do the same.

[Rrumbler]

That's the way my 2002 Toyota Tundra V8 does; related to temp/speed.  But, I don't know why.

[chimp koose]

If you lug a cold motor it will probably use more fuel not save it as is the intent of the device .

[Crosley.In.AZ]

Most OEM have a parameter temp range setup for lockup to be applied.  

Too cold : lockup clutch is disabled.  

At one time, GM used a system to lock the converter up sooner when trans temp got too high.  the more modern vehicles, Over drive gear is disabled if trans is too hot.