Friends,

Maybe this is normal, but I just noticed it within the past month after 8 years and 95,000 miles. What do you think?

This month, I've noticed that when I leave my neighborhood on a flat road, the truck shifts into 4th gear at 40 mph, and the engine speed is about 1,600 rpm. Then I reach a steep hill. While ascending, the truck remains in 4th gear, steady at 40 mph with cruise control, but the tachometer jumps to about 2,200 rpm.

I figured there'd either be a downshift into 3rd, or the turbos would kick in. I wonder whether I should be worried about a transmission problem, such as a potential torque converter failure, or is this just normal and I never noticed it before? The truck drives beautifully, so if there's a problem on the horizon I'd like to get ahead of it.

Thanks!

 

Hill retard in action.
Normal before the engine fully heats up.
Same thing will happen in OD if you come to a steep hill in OD, and vehicle speeds up, the engine RPM will rise to try and keep Set speed.
If you use the brakes at this point, OD kicks off.
Only other control you have is use the Cancel button, use the Brakes to slow down, then restore the speed with the Set button.
Try it out to see.
Good luck.

 

True, the engine hasn't fully heated up at that point.

Is the torque converter slipping because the transmission fluid is still cold, or something like that? I'm trying to understand the mechanics of it.

Thank you, Bluegrass.

 

Well no its not the Torque lock up slipping because it locks up in first gear after a certain speed is attained and stays locked for all, other upshifts.
There is no need to unlock normally unless there is fault.
Why? is because unlocking causes fluid heating un-necessarily along with higher engine RPM that serves no purpose and saves wear.
Good luck.

 

Bluegrass question. What specifically IS "hill retard" if not the torque converter unlocking?

 

It's the torque converter unlocking. My 6R-80 does the same thing when I'm climbing modest hills at part throttle. It does it whether warmed up or not. Not sure why it chooses to unlock the TC instead of downshifting sometimes, but I've always considered it to be a normal feature of operation.

 

There are no trouble codes, but it's about time for a new filter and fluid. I'll start there and we'll see what happens.

Thanks, everyone.

 

This is normal when the transmission temperature is low. The truck is trying to warm the fluid more quickly by leaving the torque converter unlocked. My 6r80 seems to wait until transmission fluid reaches 70-90°f before it locks the torque converter.