Was 11* when I left my house this morning. Jumped in my low mileage '01 ram 1500 4x4 (5.9mag). No warm up, just got in and went. Trans did not want to shift into overdrive for about the first 10 minutes, then seemed to be normal after that. Is this just an issue with thick trans fluid not warmed up, or is this a sign of trouble brewing?

I wouldn't be worried about it.

10 minutes is a long time .. how cold was it? LIKE up in cAnUkAdA ?

Run it a few minutes in neutral, not park, then try it.

Normal. It's in the Owner Manual: Transmission will stay in third until the trans gets to a certain temp and then it'll catch 4th. Reason given by Chrysler? Fluid is too thick to flow back to the overdrive in the tail-end of the trans. That's how the early Overdrives burnt out: lack of oil.

Is there a way around it? Yup. Just like the old Torqueflites: set the e-brake and idle it in "neutral" while it's warming up.

yep, not programmed to engage into OD until a certain temperature is reached. Not sure if it's engine or tranny temp though.

Okay guys, thanks for the good news! I got to thinking about it, and it was probably 3 or 4 miles before it went into overdrive, so more like 5 minutes after cold start instead of 10 minutes I stated at first. It shifted normal this morning, only down in the 20's this morning.

I have driven trips of 30 and more miles in the dead of winter when temps were -30 and plus cold blowing snow and the transmission never did shift into OD.

Similar results here. Had a few early non lockup 518's that almost seemed as if it needed to get above freezing, temp wise, and I don't know where that sensor is, but they were all the same. sub zero weather would keep overdrive out until certain temp was reached.