Okay so here is what is going on, on a cold day has to be blow 50deg. So when I go out and start the truck and let it warm up everything is good. I have a very short drive to the hwy once I'm on the hwy the truck will not kick into over drive for a mile or more. Fluid is full I was thinking I may need to change it. Any thoughts.

 

It's a saftey feature. Mine doesn't shift for a couple miles sometimes. It's all good.

 

Well then, my tranny doesn't have this "safety feature" . Mine shifts into OD anytime (hot or sub-zero) I am at 38 mph (so long as the truck isn't under a load).

 

Hmmm... I posted this topic a year or two ago n the verdict was it was like a limp mode until temps came up. Both my trucks do it with lots of miles on them. Colder mornings(close to zero or below) mine won't shift for maybe five miles or more. During the summer it shifts normal. So from what I have learned here in fte its all good.

 

Sweet deal thanks for the help guys.

 

The torque converter doesn't lock until the trans warms up. It does go into overdrive cold. It was done this way because the hydraulic system couldn't control the lockup clutch with cold ATF. It also helps warm the engine so that there is heat in the cab sooner.

 

Well said Mark.

 

Mark,does that mean nlemerise's trans is having issues? He's saying his will go into OD at speeds as low as 38?

 

Tyler it means my tranny (a JW unit) is working just fine. The OP stated "I'm on the hwy the truck will not kick into over drive for a mile or more." Mark wrote "It does go into overdrive cold." Mark stated the torque converter does not lockup when cold. My guess is that the OP and yourself may be mistaking the lack of torque converter lockup for a failure to shift into overdrive when it is cold outside. Somewhere I saw an LED install to show when the TC locks/unlocks. I'll see if I can find it.

Here is a page by Guzzle on the concept of an indicator light for the TC (as part of a manual lockup switch).

 

Ok,I understand now. Thanks

 

Easy way to tell the difference. When it won't "shift into overdrive", press the OD off button on the shifter. It the trans downshifts, it's in OD and the TC isn't locked. If nothing happens, it is not in OD. Mine does the same thing on cold mornings.