Jake Braking A 5er Down Long Steep Incline

[Rollochrome]

Just arrived at our vacation destination yesterday.

I had my factory “jake”brake set and the cruise control on when I crested the top of the largest hill going into this part of the country. I’ve never towed a fifth wheel through this kind of environment before and felt like I was looking over the top of a roller coaster when I looked down the several mile long descent

My F350 downshifted all the way into third gear and held me at 55 miles an hour from the top of the mountain to the bottom of each mount I encountered

After I went up and down several mountains like this however it occurred to me that I might be creating conditions conducive for a jackknife if I didn’t have any braking on the trailer at all in such a descent since the wheels of the truck were providing the resistance going down the hill via engine braking and the wheels of the trailer were just rolling freely.

Do I need to be using my integral brake controller in such a condition to apply a little bit of braking to the trailer all the way from the top of the mountain to the bottom?

[Cummins12V98]

4x4ord wrote:

Cummins12V98 wrote:
It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.

170-180 reverse hp sounds like the right number to maintain 55 mph on a 5-6% grade with 35,000 gross combined weight. I think the Ram exhaust brake should be able to create that amount of braking without using wheel brakes. The advantage of using the Auto setting rather than CC is that "Auto" just works ... ie you don't really have to do any thinking about it. If you're going too fast you simply brake a bit to slow down, or, if you want to pick up your speed a little you step on the throttle a bit to get to the speed you want. If you want "auto" to help slow you down, as soon as you touch the brakes the EB goes into full on mode until you release the brake pedal. I think after you use the auto EB setting a bit you might get to like it better than CC.

Thanks for opening my eyes and I will give it a shot.

[4x4ord]

Cummins12V98 wrote:
It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.

170-180 reverse hp sounds like the right number to maintain 55 mph on a 5-6% grade with 35,000 gross combined weight. I think the Ram exhaust brake should be able to create that amount of braking without using wheel brakes. The advantage of using the Auto setting rather than CC is that "Auto" just works ... ie you don't really have to do any thinking about it. If you're going too fast you simply brake a bit to slow down, or, if you want to pick up your speed a little you step on the throttle a bit to get to the speed you want. If you want "auto" to help slow you down, as soon as you touch the brakes the EB goes into full on mode until you release the brake pedal. I think after you use the auto EB setting a bit you might get to like it better than CC.

[Cummins12V98]

It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.

[4x4ord]

Cummins12V98 wrote:
I gave the "AUTO" mode a shot. I was descending I-15 to I-215 from Barstow, I would guess it's 5-6% grade. I let off and tapped my brakes at 60 mph. It only took seconds for my speed to increase to 70. I hit the brakes and set cruise to 55 and locked in 4th. I adjusted the cruise up and down to stick close to 60.

Lighter loads may work on AUTO but 35k combined is No Bueno.

If you think about what auto EB is doing you’ll better know how to use it. Auto EB on the Ram is capable of producing exactly the same back pressure as “full on” EB which is 60 psi. The amount of braking the EB can do is a function of the back pressure x the engine rpm. If you let off the throttle at 60 mph the auto EB would have closed and been creating 60 psi back pressure. If the truck starts slowing down the auto EB would open to prevent slowing dow … it’s trying to maintain the speed you were travelling when you let go of the brake. As soon as the truck started accelerating it should have been apparent that the EB could not hold your rig back at the rpm the engine was turning. You could have locked out 6th and 5th gear. If it couldn’t hold back in fourth you could have slowed down enough to lock out 4th gear. If your truck holds back your rig in 4th gear using cc but won’t hold back your rig in 4th gear using auto EB it is because cc is applying your wheel brakes. On the Ford, auto EB will not apply the wheel brakes until the engine rpm reaches the red line…. The Ford cruise control will apply the wheel brakes shortly after the truck accelerates above the travel speed set point.

[Cummins12V98]

I gave the "AUTO" mode a shot. I was descending I-15 to I-215 from Barstow, I would guess it's 5-6% grade. I let off and tapped my brakes at 60 mph. It only took seconds for my speed to increase to 70. I hit the brakes and set cruise to 55 and locked in 4th. I adjusted the cruise up and down to stick close to 60.

Lighter loads may work on AUTO but 35k combined is No Bueno.

[4x4ord]

ReneeG wrote:

rhagfo wrote:

ReneeG wrote:

Retired JSO wrote:
I tow in tow mode and use cruise control all the time with the exhaust brake engaged. The OP has a 2019 F-350, I have a 2018 F-350, my exhaust brake has no auto, it’s either on or off.

We have a 2011 F350 and the true engine compression brake (not exhaust) is only off or on with setting the Tow Haul Mode.

I agree with Ron, please explain all recent HD pickup use an exhaust brake, which uses some means of restriction of the exhaust gases.
Now PacBrake offered a Load Lash device for the Cummins 6.7, that was more like an engine brake.

It's not a true exhaust brake, but merely uses the transmission and the back pressure of the engine. It works and it's efficient, but Ram owners , I beleive, have true exhaust braking.

The 2011 through 2014 Powerstroke didn’t have an EB switch but did have a turbo that was capable of creating some back pressure. In 2015 the Powestroke turbo was upgraded, an EB switch was added and the EB performed considerably better. The Cummins EB works very similar to the Powerstroke in that it is the turbo that is creating back pressure. However, because Cummins engines use stronger exhaust valve springs the EB can be used to generate higher back pressure without danger of the exhaust valves “floating” and coming into contact with the pistons. For this reason the Cummins can generate the same negative horsepower at 3000 rpm that the Powerstroke can at 4000 rpm.

[Cummins12V98]

I will give it a try tomorrow going from Bakersfield over Tehapi Pass.

[Rollochrome]

I am learning a LOT here

Thanks to all of you

[4x4ord]

So long as you have a steep enough hill and or enough weight pushing you the auto EB will develop full back pressure during grade braking. Full on vs auto will not make any difference with a heavy trailer on a steep grade. If , during grade braking, cruise control holds your truck back better than auto EB does then it is because CC is applying your wheel brakes.

If you are using your EB to slow you down …. full on is the better choice. If auto is selected during deceleration the EB will do very little unless your foot is touching the brake pedal.

[blofgren]

4x4ord wrote:

Cummins12V98 wrote:
Auto mode is useless unless you are towing a lighter RV and smaller grades at least with RAM trucks.

I also set my cruise control at a lower speed to maintain the actual speed I want. It varies depending on how steep the grade is. I also on steep grades select the gear that puts me up near the redline for best braking.

I am glad I don't have the ability for the truck to apply my trailer brakes. I like controlling me descent with cruise and proper gear selection for the grade. I never use Auto mode, I have tried but found it useless for my large load.

Could there be something wrong with your truck? The EB on the Cummins should generate 60 lbs of back pressure on a steep grade with a heavy load regardless of whether it is set to auto or full on.

I think his load is 33-36,000 lbs so I don't think there's anything wrong with his truck. 😉

I too only use full exhaust brake mode with my truck.

[4x4ord]

Cummins12V98 wrote:
Auto mode is useless unless you are towing a lighter RV and smaller grades at least with RAM trucks.

I also set my cruise control at a lower speed to maintain the actual speed I want. It varies depending on how steep the grade is. I also on steep grades select the gear that puts me up near the redline for best braking.

I am glad I don't have the ability for the truck to apply my trailer brakes. I like controlling me descent with cruise and proper gear selection for the grade. I never use Auto mode, I have tried but found it useless for my large load.

Could there be something wrong with your truck? The EB on the Cummins should generate 60 lbs of back pressure on a steep grade with a heavy load regardless of whether it is set to auto or full on.

[philh]

2022 F350D adaptive cruise, driving from MI to FL,

Truck will downshift to hold speed going downhill. If that isn't enough, then EB kicks in, if that isn't enough, then the brakes are applied. It held downhill speed to 0 to + 2 mph. Uphill was a different story, it would drop to -5 before aggressively downshifting and getting deep into the power to bring the speed back up.

[ReneeG]

rhagfo wrote:

ReneeG wrote:

Retired JSO wrote:
I tow in tow mode and use cruise control all the time with the exhaust brake engaged. The OP has a 2019 F-350, I have a 2018 F-350, my exhaust brake has no auto, it’s either on or off.

We have a 2011 F350 and the true engine compression brake (not exhaust) is only off or on with setting the Tow Haul Mode.

I agree with Ron, please explain all recent HD pickup use an exhaust brake, which uses some means of restriction of the exhaust gases.
Now PacBrake offered a Load Lash device for the Cummins 6.7, that was more like an engine brake.

It's not a true exhaust brake, but merely uses the transmission and the back pressure of the engine. It works and it's efficient, but Ram owners , I beleive, have true exhaust braking.

[rhagfo]

ReneeG wrote:

Retired JSO wrote:
I tow in tow mode and use cruise control all the time with the exhaust brake engaged. The OP has a 2019 F-350, I have a 2018 F-350, my exhaust brake has no auto, it’s either on or off.

We have a 2011 F350 and the true engine compression brake (not exhaust) is only off or on with setting the Tow Haul Mode.

I agree with Ron, please explain all recent HD pickup use an exhaust brake, which uses some means of restriction of the exhaust gases.
Now PacBrake offered a Load Lash device for the Cummins 6.7, that was more like an engine brake.