Diesel Question

[martinajm]

Can you please explain why I wouldn’t want the diesel to downshift in that situation?

Or how one would even do this? As far as I know, there is no way to prevent the downshift unless you VERY SLOWLY apply petal pressure.

 

[StephenPT]

Or how one would even do this? As far as I know, there is no way to prevent the downshift unless you VERY SLOWLY apply petal pressure.

Just set cruise control at your desired speed and the truck will do the rest. I have a Banks I-Dash and on my towing layout I have the gear indicator. On flat ground going 62mph it's in 9th gear. Light grades it will stay in 9th, but eventually downshift to 8th and then 7th if it really needs to on a steep grade. I think one time I had it go into 6th and that was a steep grade. The engine monitors the load %, speed, rpm, etc. and determines the best gear for the situation. Watching the gear indicator while towing and not towing, this engine does NOT downshift until it absolutely needs to.

The 3.0 Duramax produces 80% of its torque at 1250rpm and 100% of its torque at 1500rpm.

 

[martinajm]

On the diesel, you do not want to downshift to pass or accelerate. Just apply more fuel petal pressure and let the lower RPM torque contribute to acceleration. My 2023 Yukon Denali Duramax is great on the highway and I have no complaints about acceleration when pulling out onto road into traffic or when passing.

Just set cruise control at your desired speed and the truck will do the rest. I have a Banks I-Dash and on my towing layout I have the gear indicator. On flat ground going 62mph it's in 9th gear. Light grades it will stay in 9th, but eventually downshift to 8th and then 7th if it really needs to on a steep grade. I think one time I had it go into 6th and that was a steep grade. The engine monitors the load %, speed, rpm, etc. and determines the best gear for the situation. Watching the gear indicator while towing and not towing, this engine does NOT downshift until it absolutely needs to.

The 3.0 Duramax produces 80% of its torque at 1250rpm and 100% of its torque at 1500rpm.

My comment about how to do it was based around "apply more fuel petal pressure" but not downshifting. Applying more pressure usually results in a downshift.

My experience with using cruise control while towing is vastly different than yours @StephenPT . I tow a relatively heavy and tall (alot of drag) boat at highway speeds. I usually lock out 10th gear. I find that when using CC that the transmission is searching for gears quite often. Without CC, I can control the shifting with petal pressure pretty well. This obviously results in more speed variability vs CC, but I figure it is better on the transmission.

 

[JayceeP]

Can you please explain why I wouldn’t want the diesel to downshift in that situation?

Low end torque… it pulls very well at lower rpm’s…. Different than a gas engine. You’d need to test drive it to understand but these trucks rarely downshift on the highway unless you smash the pedal. Up and down moderate hills…. Very little downshifting.

 

[Fless]

What's the diff between a flower petal and a fuel pedal? (Rhetorical question)

If I sold flowers and car parts would I be a peddler of petals and pedals?