Freightliner auto transmission on steep down grade

Very well written. And exactly on point.

I do have to point out...

Issues aren't on days when you can use cruise control and coast, they're on the heavy rain/snow/ice days. Then it gets fun

 

Manual transmissions with servos, motors, computers etc become a automatic transmission. Software then proceeds to run it.

I run the mountain at 50 the same as I did at 21, regardless of auto or manual. And especially with auto in manual mode and the jake brake balanced against the downgrade at a speed designed to take her all the way down without touching the brakes once.

Anyone who smokes brakes did not do the downgrade correctly. (I used to until I learned.)

I understand the procedure for computer control in cruise downgrade etc and how to do it, I never allowed that truck the chance. It's manual all the way down. Every time. Fuel mileage really is irrevelant, fuel burn is a certain amount and cold brakes ready for real work if necessary.

Call me stubborn. But when Im 100, I'll run the #### hill the same way, I don't care if it is a million pounds.

 

What the OP says is true, for the most part.

There are some steep grades that the cruise simply can not handle with a heavy load.
In that case you just have to set the engine brake to maximum and brake when you need to.
And I have noticed that doing so will sound an over-rev alert, even when staying within the range the cruise control normally uses.

The DD-15 / DT-12 combo thinks nothing about 2200-2300 RPM when engine braking down a hill while on cruise control. But if I let it get that high off the cruise control it has a heart attack in short order.

 

Setting the cruise control will work. You can do the same thing yourself and switch from stage two and three also. Plus drivers can feel more in control maybe the shift point is 1800 for stage three so just switch to stage two and the transmission won't change gears below 1800 RPMs

 

Mine won't upshift even if I am at 2500 while on a downgrade.
It does all it can to slow me down, not the other way around.
If it gets below a certain RPM it will downshift to maintain the best engine braking possible.

 

Again, as stated in other forums, I disagree. I haven't come across a grade that is too steep for the DT12 in cruise control mode.

It's just like a manual transmission; you need to be in the correct gear/speed.
In a manual, you choose the gear to go down, which will determine your max speed in that gear. With the auto, you choose the speed you want to go down, set the cruise below that, and the computer will determine the gear.

As OP said, you can manually apply engine brakes to get more stopping power, than flip it back into auto mode.

It may, however, take you 1-3 times of going down that particular grade to figure out the right speed, just like the 1st time you go down any grade in a new truck or even if you're just starting out.

I do all grades in cruise on the interstate system. I don't take many secondary highways, so I cannot testify for those grades, but I haven't come across one yet that can't be done in cruise.

Of course, this is on dry roads.

 

If I am ever on a hill/mountain that I haven't been on before, I still stick with the old rule, go down in one gear lower than you came up, always worked for me?

 

Errr....can you 'splain this again?

I only have 2 pedals (brake & throttle) in my Cascadia with DT-12 automated transmission