It'll shift into OD on first startup and start driving when the air temperature is really cool to cold. But after the engine gets to operation temperature and i come to a stop at a light or sign and take off again, it won't shift on up again. 

It will, however, shift up when I disengage the OD, essentially, shifting into gear 3.5. 

Well, I can putt around town and get to where I'm going within a reasonable about of time with a few extra minutes added, I just figure in leaving a little earlier. 

Then, on the hotter days of this year, I'd forget to disengage the OD and it'd shift into 4th and stay there until I came to a stop again. 

As long as I was moving, it wouldn't come out of 4th. 

Even the real cool spell earlier this week, it wouldn't shift into 4th, no matter how much I'd throttle tease it up and let off the gas. 

So, back to gear 3.5. 

At times, it'd shift on it's own to OD when I'm just dinkin' along on low rpms and a slow take off and no hurry. Other times, NOT. 

Getting around at 45-50 isn't so bad as it sure saves on the gas as it'll do 15mpg consistantly in the 1700-1750 rpm range, which is where I try to keep it, unless I've just "got" to be somewhere. 

Thanks again for any and all input of what and where to start looking. 

BTW: had the transmission rebuilt about 70,000 miles ago at 304,000 miles.

It rides real nice and I'd like to take it on road trip as needed. 

It'll shift into OD when it's real cool outside or on occasion when I'm driving real slow but hardly never if it's hot out. 

But then, make a liar out of me like it did the other day when it was 90* + and it shifted into OD, just like it was supposed to. 

The intermittent shifting into OD is what has me scratching my head and why I'm asking questions here, given this behavior. 

It's not shifting in & out constantly, either it will or it won't. 

If it won't, I'll disengage the OD and it'll shift up that "half gear". 

I suppose you could say that the converter isn't locking up to get it to shift into OD, if my concept is correct. Maybe not, though. 

I just know that it'll shift normal in the 1st 3 gears, and maybe it will - maybe(more than likely) it won't, shift into OD. 

I'm not "that" schooled in automatic transmissions yet, but getting there.  So, I'm asking here. 

You know the model/year, have the vin #.  Go to youtube and google, and ask the same questions.  Lotsa times, the question has been asked, before, and you'll find a video of how to fix the problem. Or the search engines may lead you to clues/symptoms, that lead you in another direction...

I definitely don't do any dinkin' around OKC. Main traffic lights are a mile apart and the traffic doesn't take their time neither. 

Amos, thanks for the starting point to look into. 

Dave, I'll do that. 

My transmission issue has been narrowed down to the PCM not telling the transmission to upshift into OD. 

They cleaned the ground connections first - nope - then serviced it - not that either. 

They did find some brass shavings in the pan when they dropped it to service it. 

Upon checking mileage, it's actually been 62,xxx since 3/2014 when it was totally rebuilt and a new PCM put in. 

It's at 366,4xx miles now. 

My previous number was a guesstimate as best as I could when I initially posted this. 

Sidenote: Ask your question in the address bar - in my case - PCM for a 96 Dodge Ram 1500 - and up popped quite a few result sites for a replacement/repair at very reasonable prices with warranties! Take your pick at the best bang for the buck!