After doing several searches of the truck’s manual, (both the print and .pdf) I could not find any specific references regarding the use of the engine brake while towing. I have “tested” this condition over several road trips. I do not know if the “condition” is unique to my truck or if it’s the same with all 2020 F350 trucks.

I am transitioning from Southern California to Southern Oregon. I use a Carson 16 foot enclosed car trailer with standard electric brakes with load range D radial tires. I have “registered” the trailer via the selected menu on the truck’s display. The empty weight of the trailer is 2030 pounds. Typically the combined weight when hauling is 7k pounds. The GVRW is 10k.

This is what I am experiencing: While towing on a down hill grade, engine brake ON, when the engine brake engages to assist with controlling the truck’s speed- the truck’s braking system is NOT engaging the electric trailer brakes. The trailer basically pushes the truck creating a hazardous condition. Interestingly, if I use the Adaptive Cruise Control set to a safe speed, the electric braking system engages and both the truck brakes and trailer effectively controls the descent down hill speed. Changing and selecting the tow/haul mode does not change the lack of electric brake engagement. Actually none of the selectable modes cause electric brake engagement. I have not tried the Hill Descent Mode button. That mode does not work for speeds above 12mph

During night driving when I manually or the Adaptive Cruise Control engages to slow the truck to the selected speed, I can see the reflection of truck’s tail lights on the front of the trailer. When just the engine brake is engaged, the brake lights do not come on.

There is one more “test” in the future I can do and that’s using a volt meter to monitor the 12v at the trailer brakes. With the massive amount of FTE member knowledge, rather than trying a dealership service, I thought maybe someone could chime in and educate me. Thanks

 

That is definitely something Ford could do a lot of improvement on for sure.

 

Pretty sure engine braking is about using the engine (and transmission) to provide braking/speed control. If you want the disc brakes on the truck and the electric brakes on the trailer to engage, use the brake pedal.

I am 4000 miles into our current trip with 2020 f350, pulling a 9000 lb. Trailer. We've had many roads ranging from 4 to 10% grades and the engine brake is working great, very rarely am I needing to supplement with the brake pedal.
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This. Doesn't sound like anything is wrong with your truck. Your truck and trailer brakes won't engage unless you press the brake pedal (not counting ACC).

Engine braking (exhaust braking) is just that. When you let off the throttle, the vanes in the turbo close to provide engine backpressure, which slows the truck, and/or provides resistance while going downhill. A big enough load and/or a steep enough hill can override the exhaust braking abilities, which means you will need to supplement it with the service brakes of the truck & trailer.

 

nothing is wrong, engine braking and tow haul are designed to help control the speed during the decent so you don't have to use your brake and over heat them.

that does not mean no braking is required.

Tip, when decending, once you are over the speed limit by an estimated 5 mph, hit the brakes failrly hard and slow it down to 5 mph below, then off the brakes and repeat as needed.

The idea so to use them, get off them and let them cool back down.

Now keep in mind, your load is not significant but if it were, that is the procedure.

Also starting your decent at no more than the speed up the hill.

 

I think we are having the same problem. I started a post “cruise control at redline” concerned basically with the same thing you are.
My truck is downshifting trying to maintain speed down hill with or without trailer, downshifting sometimes to the red line.
my tuck is 2020 7.3, with 10 speed.
I always though cruise used engine braking and brakes to maintain speed. I am taking it to the dealer when I get back home.

 

So, lets clear up a few things here.
I see in your signature that this is a 6.7 powerstroke truck.
There is no "Engine Braking", but there is "Exhaust Braking" available, turned on via the center stack switch.
The exhaust brake has nothing to do with the engagement of the trailer brakes.
The trailer brakes are controlled by the trailer brake controller, which is in turn engaged when you step down on the brake pedal.
And, the trailer brake controller is the little black unit on the lower left side of the center stack, it has two buttons + and - and a slide switch.
The + and - buttons control the "Gain" setting, which controls how strongly the trailer brakes will be applied.
The slide switch on the controller is used to manually engage the trailer brakes separately from the service brakes on the truck.
Now, as you've discovered, adaptive cruise is the only mode where the trailer brakes will be automatically applied by the truck along with the truck service brakes and the exhaust brake.
So, basically, your truck is performing completely normally, there is no issue except that you didn't understand how these systems work.
Now, you do.

 

Which exhaust brake mode are you in? Automatic of Manual? Automatic is two presses of the button, manual is one. You get more turbo action, and therefore more "braking" in the Manual mode. On steep downhill runs, I use Manual mode of the exhaust brake and usually also use the Manual mode of the transmission, selecting which gear to be in.

Automatic exhaust brake mode works. It's just doesn't fit as well with the mountain passes I go over.

Side note: I have an issue with my 6r140 transmission where once tow/haul and/or the exhaust brake downshifts to 3rd, it won't upshift without a lot of RPM's. When I use the Manual transmission mode I don't have that issue. At the top of the hill I shift to Manual mode so I don't have to do that in the middle of the downhill portion.

 

IMO, The engine brake design and application is right.
I definitely do NOT want my engine brake controlling the wheel brake system. It’s a separate system and it should stay separate. I prefer to use foot brakes as little as possible when towing, and prefer the engine to do the work first until the foot brake is needed.

 

Not an engine brake - not an exhaust brake - it is a turbo brake, manipulating the vanes in the VGT, variable geometry turbo.

Did you know you can tap the turbo brake button twice?
First tap turns it on, second tap sets it in auto mode. The difference is poorly documented in the manual. But on my truck in auto it uses the service brake sin addition to the turbo brake. Something to look for next time out towing ( i haven't tried it yet)is to bring up the screen that shows the towing info displaying the forward/rearward and side to side attitudes, that screen also shows the trailer brake controller gain as it is being applied.

Instead of a voltmeter or in addition to you could use a second 7 way plug and wire in an incandescent bulb and set it somewhere where you can see it in the mirror. It might surprise you when, how much and how long trailer brakes are applied.

 

It is an "Exhaust Brake", turbo brake is not the correct terminology, just that the exhaust braking is accomplished by the vanes in the turbo being closed off instead of a flap in the exhaust pipe.

 

FWIW, Ford calls it the "Diesel Engine Brake".

 

The factory exhaust brake works by closing the turbo vanes, creating an almost perfect obstruction in the exhaust flow. When the exhaust valve is open and the piston is moving upward the air is pushed against the obstruction, creating a braking force.

Don't expect it to dramatically slow your vehicle. The system doesn't develop a huge braking force.

The exhaust brake system has 2 modes, manual and automatic. The manual mode applies the exhaust brake when pressure is released on the throttle. Throttle off, vanes close.

Automatic mode (press button twice) manipulates the exhaust brake and the transmission in an attempt to keep the truck at the speed where the brakes were last applied and released. In other words, coming down a grade with the exhaust brake in automatic mode, you step on the brakes and slow to 50 MPH. Your truck will try to maintain 50 MPH by closing the turbo vanes and downshifting.

Tow/Haul mode enhances the exhaust brake with more aggressive downshifts. More RPMs equal more braking force.

 

Another note, the exhaust brake only operates when the engine speed is above 1500 rpm, and gives the most braking force at much higher rpm's.

 

Call it what you please, an exhaust brake is a butterfly valve (typical) downstream in the exhaust pipe. The big three currently use a VGT for a similar effect and it is a turbo brake.