Cold transmission shifting (1 Viewer)

[Tux318]

I've noticed this winter that my 96 doesn't want to shift into OD until engine temps hit 130F. It's like clockwork...ultragage hits 130, tranny shifts. I know the trans fluid needs to warm up. I assume this is normal....thoughts?

 

[cjmoon]

There is engine temp sensor specific for the tranny. Yes it locks out OD under normal conditions. Under certain fault modes/error lights it does by pass this function.

 

[Booger weldz]

I get off work at 4am all winter and the tranny doesn't go into OD for the first 5 miles or so. Glad to know this is normal

 

[Oscar Witte]

This makes so much sense now. I try to play with the throttle until shifts early in the morn. Guess one less thing to worry about.

 

[Tools R Us]

I've noticed this winter that my 96 doesn't want to shift into OD until engine temps hit 130F. It's like clockwork...ultragage hits 130, tranny shifts. I know the trans fluid needs to warm up. I assume this is normal....thoughts?

That is normal, from the FSM:
HINT:
O/D Gear Up–shift Prohibition Control (Coolant temp. is 55° C (131°F) or less.)

 

[Tux318]

Thanks Tools. I should have looked in my FSM. Oh well, now it's here for someone to search....and yes ultragage reads 131.7 when it shifts every time....so my truck is right on the money.

 

[cjmoon]

So one question I haven't been able to answer is if you unplug the sensor will it bypass this function ad allow OD shift at all temps?

I did a diesel conversion and thought I was going to have problems with this function. I broke the tranny temp sensor on my final installation ordered a new one thinking I would need it. Drive it the first time before installing. OD shifts with out input.

I haven't been able to confirm if this is because to computer is stuck in a fault mode that allows OD shifts or it it is the temp sensor alone.

 

[westafari]

I just started wondering about this myself recently...obviously wasn't curious enough to dig up any info. Grateful for the Mud brain trust