Steep grade braking and use of Transmission

Iggy · 09-13-2012, 03:40 PM

I found this answer when someone asked about driving down a steep grade and their brakes became very hot. I thought it was noteworthy how to use your brakes and transmission to maintain a safe speed.

A couple of general comments on going downhill in a motorhome:

Be sure that you change you brake fluid every 2-3 years. As it absorbs water (as it was designed to do to protect the iron parts of you brake system) the boiling point of brake fluid decreases from close to 500 degrees F to 286 degrees F! Temperatures in your calipers under extended hard braking can exceed 286 degrees.

The proper use of your service brakes while descending a grade is to NOT USE THEM. They are not there to help you maintain a safe speed of descent. They are ONLY to be used to slow you down enough to "grab a lower gear." Though your coach weighs many times what your car weights, brake surface area (dictated by size of wheels) is only slightly larger than on your car.
So a very different driving technique is needed.

The correct gear to descend a grade is the gear that holds your speed in equilibrium. That could mean 1st or 2nd gear, even if the road is dead straight for 10 miles. If you find that your speed is increasing, firmly apply the brakes enough to slow down enough to "grab a lower gear." Physics dictates that your equilibrium speed is slower than an empty 18 wheeler and faster than a loaded one.

We assume that your toad has brakes as well. Your chassis brakes were not designed to stop the weight of the coach AND the toad.

If you drive properly, you will not wear out coach brakes -- we have 158,000 miles on original brakes and have driven a LOT of serious mountain roads.

manvel · 09-13-2012, 05:32 PM

I use the tow haul,it works great,when you push on brake the tow haul will gear down for you, came down some steep hills from Red River NM.Did not have to use brakes much.But I did get passed by a women on a bicycle going down a 25 MPH speed limit .

joelek · 09-13-2012, 05:35 PM

How many gears you got in a motorhome coach? Does it have a tow mode button like a pickup that uses engine braking? I've never driven a coach bus before.

I've driven 9 and 10 speed Eatons in a semi - Volvo and International. I like all those manual gears for control but people tell me the new auto transmissions in semis work for mountains rather well. I suspect a big coach RV/Bus would be the same or close to it anyway.

Iggy · 09-13-2012, 05:46 PM

Quote:

Originally Posted by joelek

How many gears you got in a motorhome coach? Does it have a tow mode button like a pickup that uses engine braking? I've never driven a coach bus before.

I've driven 9 and 10 speed Eatons in a semi - Volvo and International. I like all those manual gears for control but people tell me the new auto transmissions in semis work for mountains rather well. I suspect a big coach RV/Bus would be the same or close to it anyway.

The Ford F53 chassis with the V10 has the Ford 5 speed with Tow Haul mode just like in the older Ford Trucks. The newer F-250 have 6 speeds.

Iggy · 09-13-2012, 05:48 PM

Quote:

Originally Posted by manvel

I use the tow haul,it works great,when you push on brake the tow haul will gear down for you, came down some steep hills from Red River NM.Did not have to use brakes much.But I did get passed by a women on a bicycle going down a 25 MPH speed limit .

Yes I use the Tow Haul mode but it seems so many don't know how to use it or active it ptoperly and Ford doesn't really spell it out clearly in the manual.

Does anyone have a better undertsanding of Tow Haul mode and have any documentation on proper usage?

elind · 09-13-2012, 06:36 PM

I was taught to downshift to a gear the will hold the speed you need to maintain going down hill. When your speed goes beyond that speed then use your brakes to slow it down to 5MPH under your desired speed. Then let your engine do the braking again. Repeat this all the way down the hill. This way you have brakes that stay cooler and keep them from fading later on down the hill.

fbconsults · 09-13-2012, 10:48 PM

Iggy, I have found that if I set the cruise control and in tow/haul mode, when I start downhill, the transmission will downshift to hold that speed. For example, coming down Halloran Summit on I-15 to Baker, I set the cruise control at 50mph, and the trans will hold it. On steeper grades, sometimes I have to brake a little to keep the proper speed.

Even without the cruise control, in tow/haul, two applications of the brake will "set" the transmission to maintain that speed that you braked at.

You probably have already learned that, but it works for me.

Forrest

49 34 · 09-13-2012, 11:19 PM

Quote:

Originally Posted by elind

I was taught to downshift to a gear the will hold the speed you need to maintain going down hill. When your speed goes beyond that speed then use your brakes to slow it down to 5MPH under your desired speed. Then let your engine do the braking again. Repeat this all the way down the hill. This way you have brakes that stay cooler and keep them from fading later on down the hill.

X2

cfsoistman · 09-14-2012, 06:04 AM

Quote:

Originally Posted by elind

I was taught to downshift to a gear the will hold the speed you need to maintain going down hill. When your speed goes beyond that speed then use your brakes to slow it down to 5MPH under your desired speed. Then let your engine do the braking again. Repeat this all the way down the hill. This way you have brakes that stay cooler and keep them from fading later on down the hill.

X3

Whenever I hook up my car to the coach I always use the Tow / Haul feature.

mkillora · 09-14-2012, 06:36 AM

A trucker's rule of thumb is to use the same gear going down the hill as you used going up it.

joelek · 09-14-2012, 07:27 AM

Quote:

Originally Posted by elind

I was taught to downshift to a gear the will hold the speed you need to maintain going down hill. When your speed goes beyond that speed then use your brakes to slow it down to 5MPH under your desired speed. Then let your engine do the braking again. Repeat this all the way down the hill. This way you have brakes that stay cooler and keep them from fading later on down the hill.

Same here - right out of the CDL manual.

Falcon35 · 09-14-2012, 05:53 PM

X 4

Nutmeg · 09-14-2012, 09:41 PM

My understanding is Tow/haul is for use on hills- Going up it will hold the transmission in gear as long as possible to prevent unnecessary down shifts. Going down hill it will provide engine braking and if you quick tap the brakes will manually downshift a gear for more engine braking. On the flat, no advantage but in life I like it in stop and go traffic.

trell · 09-16-2012, 02:25 PM

New at this only had MH a couple mos. 2001 V10 FORD 33.6 georgetown,tran has 1-2-D and overdrive.
We pull a trailer w/victory vision m/c on it total 1250# pulling. We have pulled it a couple time felt like we weren't pulling anything. Going to FL in oct. for a while do you think we will have trouble stopping this rig in the smoky mountains?What must I DO going down a hill or up for that matter?
P.S. the brake have been check out and found to be good. seem to stop alright.

trell · 09-16-2012, 02:35 PM

What is this tow/ haul mode you speak of?

Campster · 09-16-2012, 02:41 PM

I have a newer (2011) Dodge diesel. When using tow haul mode along with turning the engine braking on there is absolutely no reason to even touch your brakes much going down hill. I was amazed at not having to use the brakes much with my first pull with this truck and our trailer. You can also manually upshift or downshift through each of the six gears of the automatic transmission. I use very little braking while pulling the trailer, should help with brake wear on both the trailer and the truck.

abjb · 09-17-2012, 09:22 AM

Quote:

Originally Posted by trell

New at this only had MH a couple mos. 2001 V10 FORD 33.6 georgetown,tran has 1-2-D and overdrive.
We pull a trailer w/victory vision m/c on it total 1250# pulling. We have pulled it a couple time felt like we weren't pulling anything. Going to FL in oct. for a while do you think we will have trouble stopping this rig in the smoky mountains?What must I DO going down a hill or up for that matter?
P.S. the brake have been check out and found to be good. seem to stop alright.

“Tow Haul” will help.
2 quick taps of the brake will tell the transmission to down shift.

DO NOT shift into 2 or 1!

ab