Tonight was the 2nd time in a week that i got on the highway after work and my truck was not shifting up to its high gear after 100km/h.
I usually have to give it a little bit while merging but don't get the RPM over 4000, but after i merge and ease up on the gas the truck will not shift out of that gear. It has only happened on the coldest days here and seems to rectify itself once the truck is up to temp.

Could this be a problem with a sensor in the tranny or could it just be that the fluid is too thick when its cold? please bear with me this is the first automatic i have owned in over 10 years of driving.

truck is an 07 ST with the 3.7 obviously

 

I would take a look at the trans fluid and filter. They may need to be changed.

 

Mine was not shifting into high gear on a recent trip to Indiana also. The temps were cold. Might just be something in the programing. Now that i have my Superchips I hope that issue will go away.

 

Yes Sir, that fixes about 80% of issues with the 545-RFE. They get picky without fluid changes.

 

If you are refering to the trans not going into overdrive. I read someplace in the ownersmanual or service manual that there is a sensor that will keep that from occuring until up to operating temp.

 

The trans has an open loop and closed loop mode just like an engine.

During cold operation, the trans has a specific shifting schedule until it reaches the predetermined temp.

How long are you driving the truck before you get on the freeway? I get on the freeway about 3 miles away from my house and by then the truck goes in to OD. Going 40mph though to get out of my neighborhood, the trucks RPMs sit around 2200 and if its cold, they dont go down until I almost hit the freeway.

 

the highway is less than a minute from my house and my work so the truck is definitly cold. I will be changing the fluid and filter anyways though just for peace of mind.

Any issues running synthetics like Redline or Royal purple?

 

The transmission requires ATF+4 which is a synthetic. I know you can use Amsoil ATF.

Try starting your truck 5 minutes early before you leave and see how the truck shifts. Even if you dont drive it, the transmission will still warm up a little while in park. It may just be normal operating since you get on the freeway so quick.

 

mine does it too when cold, its some sort of safty feature for the trans untill the fluid gets to temp, but get to the fluid and filter soon as you can, it's never a bad idea

 

nope i run royal purple and it shifts so much better then it used to!