Down Hill Braking on a Ford Chassis

Falcon35 wrote:
The new Ford transmission with tow haul program works something like an exhaust brake. When I approach a steep hill I punch the tow haul button and when it starts to speed up I push the brakes and it down shifts. I have traveled some roads with some real steep hills and have not had any problems.

Exactly how mine works, seems pretty effective

..As already indicated, a gas engine's throttle plate and vacuum it creates naturally gives it very good engine braking, without having to add an exhaust brake like what is required with diesels.

This is a subject I always find very ironic - people think diesels are so much better for their engine braking, when reality is the exact opposite - diesels engine technically has ZERO engine braking by themselves. They have to have a device added to choke up the exhaust to slow it down. A gasser OTOH, naturally has good engine braking with the vacuum created by its throttle plate. No need to add something to it that chokes the exhaust to give it braking like you do with a diesel.

..All that said, the tow/haul mode on the torqueshift tranny Ford uses with its V10 gasser in the F53 chassis, works very good. It utilizes the V10s NATURAL engine braking by downshifing very well. I'm very happy with it. When descending a steep hill, I just turn on tow/haul mode, and tranny automatically downshifts as approprate to keep speed down. Pretty much, when you let off the throttle in tow haul mode, it immediately downshifts and slows things down.

Just got back from a trip to So. Utah (Lake Powell), going into Bullfrog there is an 8% downhill grade of 4 miles. I have an 2002 Itasca Sunrise with the Ford v-10 and Allison transmission. I was pulling a Jeep Wrangler. I am also an advocate of anticipation, keeping my speed in control by using short periods of brakes with longer periods of no-braking in between. Also took the overdrive off which keeps the rig in a lower gear, didn't have any problems.

I have no idea about the mechanics of it but the Tow Haul feature works great in the mountains.

BillMFI,
Tow-haul does not take the tranny out of overdrive. you have access to all 5 gears. All it does is hold gears a little longer for more torque before it shifts into 5th gear. It just changes shift points. And add grade braking, of course.

ditto on the tow/haul mode. This takes the tranny out of overdrive which is a good idea on even moderately steep hills. Tap the brake once and you go down one gear. Tap it again and you go down another gear. I hardly ever use my brakes even on steep inclines. I often use this same procedure on Interstate exits that have short slow down lengths and/or steep curves. I also use tow/haul on roads that have short steep rolling hills that cause the overdrive to suddenly drop two gears for a short climb with resulting high loud rpm increases.

chuckftboy wrote:
I also drive the F-53 and find no problem down a steep grade using the tow/haul feature with electronic control does a great job.

X2, I have yet to use tow/haul outside of towing. Brakes and tranny braking work great for me.

I just got a 2011 Itasca Sunstar 36D and I have driven diesel trucks with Allison and turbo brakes and I had a Holiday Rambler Endeavor 40PDQ with a 400 Cummings engine and I have to say that this F53 with the Ford Torqshift impressed the heck out of me going up and down an 8 degree mountain to Boone a couple weeks ago(our first trip with it) I was worried about power and grade breaking and it was a moot point. It towed a Prius on a dolly and the grade breaking worked as well as the Allison's and the engine break on the Endeavor. I put it on Tow-Haul mode and let the tranny do it's work. I never even downshifted manually down the 4 mile 8 degree mountain road, the tranny did it all for me and held the 30MPH even while hitting about 5000rpms. I'm a believer.

wolfe10 wrote:

Terryallan wrote:
A diesel just free wheels downhill in any gear, unless it has some sort of add on braking. Where as a gas engine has compression on the back side naturally, and will in fact hold the vehicle to a lower speed, IF you down shift.

Actually, compression is NOT why a gasoline engine has better engine braking than a diesel. Remember, a diesel has HIGHER compression (usually around 17:1) than a gas engine.

The difference is that a gasoline engine has a THROTTLE PLATE, so there is a significant vacuum on a gas engine with the throttle closed. The pistons have to do a lot of work to pull the piston down against the vacuum of closed throttle plate.

There is no throttle plate that the piston has to pull against with a diesel engine.

Which is why I said on the back side. Diesels have tons on the front side, But none on the back side.

Terryallan wrote:
A diesel just free wheels downhill in any gear, unless it has some sort of add on braking. Where as a gas engine has compression on the back side naturally, and will in fact hold the vehicle to a lower speed, IF you down shift.

Actually, compression is NOT why a gasoline engine has better engine braking than a diesel. Remember, a diesel has HIGHER compression (usually around 17:1) than a gas engine.

The difference is that a gasoline engine has a THROTTLE PLATE, so there is a significant vacuum on a gas engine with the throttle closed. The pistons have to do a lot of work to pull the piston down against the vacuum of closed throttle plate.

There is no throttle plate that the piston has to pull against with a diesel engine.