between pulling in tow haul and using engine braking (EB)? And should I use just one singularly or both simultaneously?

If I'm in my truck its pulling - and I always activate tow haul; but the other day I was in some short/ 8% climbs (then downhill of the same stuff) very twisty roads - so I activated EB. From my perspective they performed about the same in controlling my descents. I can say that (while using EB) I've never before heard so many RPMs from my truck as I was going downhill.

For those interested it was somewhere between Buford, Ga and Murphy, NC - a 100 mile stretch? (maybe halfway).

 

I think that the optimal situation is to use both. With only tow/haul the transmission will downshift to try and hold speed on descents, but without the engine brake turned on you don't get any of the exhaust braking added in. With both turned on (I run my engine brake on the automatic setting) you've enabled the exhaust brake and it works in conjunction with the tow/haul mode on descents.

 

I suppose to y'all who live in this type of geography think nothing of what I traveled over, but I can typically cross a thousand southern miles with only a few hundred feet of elevation change - all with gentle turns.

On this particular road I was looking out the left side window to see the road ahead, dragging 42 feet of fifth wheel behind me; its axles were well into the wrong lane on some of these turns. On top of that there were a bunch of bikers hot-rodding this stretch.

 

Sounds pretty sporty!! I full time RV with a big fifth wheel, and use tow/haul and automatic engine braking 100% of the time. I can't think of a reason not to. Part of our departure routine is my wife asking "Mirrors out, tow/haul on, engine brake?".

 

If it weren't for the occasional stop sign at the bottom of a hill (often followed by another 100 foot climb) I don't think I'd ever use tow haul - but I've seen enough of this situation that I now routinely do; and it does well, shifting (with an engine RPM response) in reaction.

I've never pulled anything like this road before; white knuckles as I made those turns - hoping to not meet oncoming traffic. The reckless bikers were on their own.

 

Getting back to my question ...
I understand that tow haul asks the tranny to downshift - and this causes the engine RPMs go higher.

But if using EB - does the engine actually perform the braking (which from what I remember is NOT exhaust braking) and allow the tranny to remain in a higher gear?

And if all that is true, what does the engine actually do to slow things down?

One final thought, please keep your answers simple - for this simple mind (currently sipping Watermelon Vodka).

 

When I'm pulling in those situations I use the manual mode not TH.

Denny

 

"When I'm pulling in those situations I use the manual mode not TH."

Oh yes, yet another viable option (damn those crafty Ford engineers) - one which I've also never tried.
Am I wrong to think of that as a manually operated tow haul function?

 

Don’t know about your ‘18, but on both my ‘15 and ‘16, once it downshifted to 4th, if it kept building RPM’s, it would also kick the engine fan on to assist the braking effect.........yup, it would really start to howl then, but even with 18000 pushing, it would still slow it down. And remember, red line on these is at 4000, and it is a V8, which, with the shorter crankshaft, can take more RPM’s than an I6. In other words, if the tach is showing 3000-3500, you are still good. As a matter of fact, the exhaust brake is much more effective up in the higher RPM range.

 

Due to the twisty road conditions (and other users) my eyes were riveted to the road ahead of me; I have no idea of what gear I was in nor the RPMs. Even my copilot let loose a few exclamations. The only relaxed one was located in the rear seat.

 

Welcome to north GA! We have all sorts of terrain in this part of the country that most people don't know about.

 

I would use them both. The Idea is to not have to use your brakes to control the decent.

As Denny said, I that situation I would have most likely placed the truck in manual mode as I crested the hill and then maintained that gear for the decent.

 

Diesel engines provide very little natural engine braking, because unlike a gasoline engine they don't have a throttle butterfly to close down the airflow and create a vacuum. That is why diesel engines need some other device (like an exhaust brake) to restrict airflow through the engine and create significant engine braking. So you really need to have the EB on to get significant braking from the engine, even with the tow/haul mode engaged.

 

Tow/Haul doesn't just use transmission to slow you down, it also changes the shift points and Torque Converter behavior (locks up quicker). I think NOT using T/H when towing heavy will cause premature transmission wear and possibly additional heat build-up. Just be careful using T/H if the roads are a bit slippery. You could lose traction when it downshifts. I use both T/H and EB when towing my 5th wheel, 100% of the time. As for manual gear selection, I dont mess with that much, the transmission does a pretty good job deciding what gear it wants to be in.

 

[QUOTE=djousma;18848226]Tow/Haul doesn't just use transmission to slow you down, it also changes the shift points and Torque Converter behavior (locks up quicker). /QUOTE]

I think that changing shift points and locking up the converter still qualifies as using the transmission to slow you down. My point is that the EB makes the engine a much more effective brake as well, working in conjunction with the tow/haul mode and the transmission.