[caulk04]

Trans temp must reach 80º before it will lock the TC.

Here is a snap shot of the shift schedule for the 45RFE from my FSM.

http://www.dakota-durango.com/forum/attachment.php?attachmentid=34731&d=1255523763

BTW - The EMCC you see in there, is the TC clutch lockup. P prefix is for partial lockup, F is for full.

 

[caulk04]

I know this is a different vehicle entirely, but my ford does this, it's recently been in the 20's, and low teens at night, my truck will sit for 15 hours, when I start it in the morning, and plop it into gear, reverse will work to back out, put it into drive, it will go, and then nothing, throw it in N for a few seconds and back into D and it's fine. I have found that warming the truck up in N has eliminated the problem. Once again, different truck/trans/motor entirely.

Try letting it idle in neutral for a min or two before you get going. Could just be cold fluid being slow or something leaking back and the system needing to prime.

 

[caulk04]

It's your TC lock. Read the temp chart I posted.

It's got to be super fucking cold to not engage OD. Count the shifts, I bet it goes 1, 2, 3, 4....wait while cold, then TC lock and 5th.

That said, the way this trans shifts, it locks the TC in 4th, then shifts to 5th. 4th and 5th gears are both overdrive (.75:1 and .67:1).

If you want to check whether the TC is locked or not, touch the brakes lightly while you're driving. When the trans sees the brakes are on, it unlocks the TC clutch. If the RPM go up when you touch the brake, the TC was locked.

 

[caulk04]

My 42re wouldn't shift into OD all the time in the winter. I've made hour long trips at 3000rpm because it wouldn't shift.

Maybe your definition of super fucking cold, and my definition of super fucking cold are different :jester:

I should hope not...according to the FSM, the 45RFE has to be below -16ºF to not engage 4th gear. Basically, it uses limp mode at that temperature. PRN and 3rd gear is all you get, unless you manually shift to 2nd.