tranny not shifting into hi when cold outside

Hello, My first winter with 2012 ram tradesman 4.7 and I have a question. When the temp dropped below 30 outside I noticed that my tranny won't shift into 6'th gear until the trans temp reaches aprox. 55 degrees. Just want to know if this is normal or should I be concerned about it?
Thank you for your help.
Bob

It's pretty common on auto trans. The fluid is so thick that it won't shift. My cars all do the same thing to a point. They'll hold a gear MUCH longer when it's cold.

Yes. This is pretty normal. A side benefit, albeit minimal, is that it keeps the engine in higher RPM's so it warms up faster.

Mine does the same thing pretty much while it's cold. Mine doesn't like shifting into 3rd easily until after I've driven a couple minutes, took me a bit to figure out why I was having shifting issues when she's cold then it hit me...fluid is thicker when cold so it's harder to move. Once it starts warming up again you shouldn't have any issue's.

actually the computer is looking at temp readings. as long as it stay below its setpoint it wont **** into sixth. it takes alot to thicken up tranny fluid becasue there isnt any detergents in it.

Thanks for the info everyone. I thought it might be the computer because as soon as the tranny temp hits 55 degrees it will shift into 6th.

Trans fluid gets very thick at cold temperatures (it can be like Vaseline® at very cold temps). The individual passages in the cooler are much smaller than the cooler lines, so thick ("frozen") trans fluid may not flow through the cooler at all, when temps are very low.

The hot oil from the torque converter is fed directly to the cooler, so if this circuit is deadheaded (due to a plugged, i.e. "frozen" cooler), the converter can quickly overheat.

A Thermal Bypass Valve (TBV) will allow flow through the cooler line circuit (bypassing the cooler), so it allows the hot oil to reach the trans sump (rather than just toasting the converter). But with basically no oil cooler, the trans will still overheat eventually. So to minimize heat generation within the converter, we use the modified shift schedule, to avoid overheating the trans. The modified schedule locks the TCC as much as possible, but when unlocked (generating heat), it maintains a lower-than-normal gear, since T/C slip (and the amount of heat generated) will be significantly less in a lower gear.

So, the TBV gets the hot oil out of the converter. The modified shift schedule prevents this hot oil (which is dumped into the sump) from overheating the trans.

The trans oil cooler is an air-to-oil cooler (not a traditional "in tank" water-to-oil cooler), so it is continually exposed to cold (ambient) air, even when the engine is warmed up. Thus, having the engine warm is no guarantee that the cooler will be "unfrozen." That's why we base the modified shift schedule on the ambient temp, rather than the trans or engine temp.