Did you check it in park, idling?

Since you just had a service, seems a month could be the time it takes for the filter screws to get loose if they weren't tight enough.

 

Yeah I checked the fluid in park idling, was full and looks like brand new fluid.

 

It should be fine with those temps. I've seen a transmission get a little slow to engage and move the vehicle when you get down well below zero, but even then it just takes a beat before it starts moving.

 

Living in igloo country my whole life and have never had one slip in the winter, even at -30.

 

You mention the trans would not "go to park" ? Not sure I follow that? If shift linkage is correct , it should shift into park? Unless you meant reverse? Could be an internal shift linkage problem if no park.

Or , if the trans is several years old, it could be morning sickness. Hard internal seals cause a loss of pressure via leaks at the internal seals inside the drums. Then the trans will drop out of gear at idle ie: neutral out. WIth an engine rev and the trans jumps back into gear , that is from low pressure to higher pressure internally.

 

Short answer, its not specifically temp related.

Coldest night I ever drove my car was -22f. Getting it started was trickier than anything the transmission had to do. That was a 20yr old 4cyl chevy celebrity. I let it warm up for half an hour, while I shoveled myself out; and then I drove an hour to get to work (typically a 10 minute drive) and the car still didnt make any heat in the cabin LOL
A Trans will shift a bit soft at 20 below, once it gets some heat, no problems usually. I have experenced the "neutral out" that Crosley mentioned, in high mileage cars.
Keep digging, you'll find it.

 

Transmission oil is pretty much like a 0W-8 or 10 in viscosity and largely is a pool of synthetics to get to behave that way. It does tire-out with age and heat to cool and back cycles and of course gears and bearings do there best to crush the molecules.

Back in the good old days of the 1960’s and earlier ATF was formulated from whale oil as mineral oil from the ground just doesn’t behave well in this application. After commercial whaling was outlawed the manufacturers of this stuff had to take mineral oil base stocks and modify them to the needs of automatic transmissions actually manual tranny’s and rear axle gear as well since most of these EP oils were based on whale stocks not gunk from the ground. Needless to say in the late 60’s into the 70’s was a hard time for highly loaded gear reduction systems. One of my first jobs in Seattle was working gear reducers for certain high speed boats that had aircraft turbines on one end of a shaft and salt water high pressure drives on the other with a transmission in between. That was a project with problems enough to drive a sober man to drink. We eventually licked it but that was more as a surviver than a conquerer.

Bogie

 

Theory: It's not hard to nick or pinch the o-ring on the filter neck when installing the filter. Possibly sucking a little air and it's worse when the fluid is thicker/colder?

 

The T-350 trans filter bolts directly to the valve body with a gasket in an OEM application.

 

So I checked again and it was little low, so I added some fluid. drove around and checked again, and now its just a tad over the F line. Should I worry and try to take some out or is a little over fine? Here is a pic i drew of about how much over

 

So I checked again and it was little low, so I added some fluid. drove around and checked again, and now its just a tad over the F line. Should I worry and try to take some out or is a little over fine? Here is a pic i drew of about how much over

View attachment 636251

So I checked again and it was little low, so I added some fluid. drove around and checked again, and now its just a tad over the F line. Should I worry and try to take some out or is a little over fine? Here is a pic i drew of about how much over

View attachment 636251

Won't hurt a thing . If it wouldn't go into park , sounds like linkage , but it's an odd occurrence.