Downshifting when going downhill question

[Ron Dittmer]

Originally Posted by twinboat

I installed a Scan Guage 2 in my old rig. It sits on the column and has a tack ( RPM ) setting.
Plugs into the OBD2 port under the dash.

Oh Yes!!!!! Great Advice.

I forgot about the ability to display RPM on my ScanGauge-II

[GypsyR]

My mistake, I was thinking 5R110W but your coach is a tad early for that and has a 4R100. Turn off the OD switch to get 3rd gear AND the coast clutch. If needed pull down the shifter to 2 or even 1 as need. The coast clutch is also engaged in both those in that transmission. But like I said before, the coast clutch is in there by design basically just for hill braking, use it!

[tap4154]

Originally Posted by twinboat

No tow haul button in 2001.

I didn't know that. Then his best option is just turn off OD and manually downshift when he needs to. In my old 2000 Ford pickup I always turned off OD when I was in the mountains. In the motorhome, never let people behind you pressure you into going too fast. Drive at a safe speed, and use the turnouts when they become available.

[pauldub]

You can do pretty much the same as you did with your Rialta. You won't care much for all the noise above 3500-4000 RPM.

[D Gardiner]

Guess I’m way more conservative on my rpm usage than most. Going down hill we put her in third, second or first gear depending on how steep the grade.
On the interstate usually we go with the posted speed limit, unless it’s a tricky grade like the Grapevine in CA. Then we will descend at the posted trucker speed limit.

We also pick a speed than is safe to descend at. If the grade is steep, and curvy, we might only go 25-35 mph, allow the rpm and speed to increase 5-10 mph (depending on conditions) then depress the brakes and slow down to our original speed. This allows the brakes to cool between applications.

[rarebear.nm]

Preserve the brakes for when you MUST have them. Man y good points made above. Always drive the mountains inside of your comfort zone. If you have white knuckles you've failed.


I learned and grew up driving in the western mountains and have been driving them for 57 years or so.



Your job is to get you, your passengers and rig up and down hills safely. Do not worry about traffic behind you. But always use a safe pullout to let the traffic pass.


I drive for what's ahead of me and adjust my speed before I get into the turns and/or step downhill grades. In turns I try make my entry to the curve my slowest and speed up slightly as I round the corner. You have better control while accelerating opposed to braking. Even more so if the roads are not dry. I tend to dislike seeing my rear end going down hill first while watching uphill! On long steep downhills my goal is to never once even touch the service brakes. That does not always work out according to plan on hills I don't know very well.



I have driven many kinds of vehicles over the years on mountain roads, diesel and gassers alike. Each have their options and use what ever is present on that rig.

[Cthecountry]

I have a 2003 GMC Sierra 1500 with an automatic transmission, 5.3 gas engine towing 2017 22ft, 5-6k lbs Kodiak tt.
I always manually down shift in the right gear at the right speed for better control and to prevent the brakes to overwork and heat up.

[GOG52]

We drive F250, 6.7 gas, 3.73 rear. Fifth wheel Cougar 327 REF, 12,600 lbs.
Tow Mode combined with Cruise control (weather permitting) keeps all in line.
In extreme grade or extreme curves we try to enter slow and keep control.
Brake when needed, but sparingly where possible.
Safety first, not out to set land speed records.
Works for us, enjoy.

[Savage1]

Originally Posted by Ron Dittmer

Hi Kip,

I have the same engine you have in our 2007 E350 chassis. I practice engine braking all the time when going down descents through downshifting. The gasoline 6.8L-V10 engine in the E450 chassis has a very high redline. The engine can spin over 5500 rpm and all remains well with it. It is loud as all heck making you feel it is going to explode, but all is well.

Unfortunately the early E450 chassis did not include a tachometer in the instrument panel, so you drive blind concerning RPMs. You might want to consider adding a tachometer to assist you with engine braking.

I don't want to be around when that V-10 grenades at 5500 rpm. not designed for that rpm.

[twinboat]

Originally Posted by Savage1

I don't want to be around when that V-10 grenades at 5500 rpm. not designed for that rpm.

It is designed for that RPM and if it was ovespeeding it would upshift.

It makes its max power at 4750 RPMs. It's a high RPM engine.

[Todd8]

Originally Posted by GOG52

We drive F250, 6.7 gas, 3.73 rear. Fifth wheel Cougar 327 REF, 12,600 lbs.
Tow Mode combined with Cruise control (weather permitting) keeps all in line.
In extreme grade or extreme curves we try to enter slow and keep control.
Brake when needed, but sparingly where possible.
Safety first, not out to set land speed records.
Works for us, enjoy.

I've been driving a gasser for 23+ years. In the last 4 yrs have found that on 6% down grades the V10 gas engine does not have enough compression to offer effective braking at 45 mph. Our combined weight is about 21k lbs. My typical approach is to brake hard to get 5 mph below posted speed limit. Then let the brakes cool until speed gets to posted and brake hard again. This has worked well on many west coast mountain passes. Do I downshift, yes when posted speed is 35 mph or less. Always, safety first, do what you are comfortable with. And remember what commercial drivers are taught, speed kills. You can't go too slow down a steep hill.

Todd8
32' 2012 Itasca Suncruiser, w/ CR-V

[Bobby F]

Originally Posted by Savage1

I don't want to be around when that V-10 grenades at 5500 rpm. not designed for that rpm.

I've seen one vehicle with that engine. The factory tachometer redlined at something over 6000rpm. I would take that as an implicit statement by the manufacturer that anything below that is fine.

[twinboat]

Originally Posted by Todd8

I've been driving a gasser for 23+ years. In the last 4 yrs have found that on 6% down grades the V10 gas engine does not have enough compression to offer effective braking at 45 mph. Our combined weight is about 21k lbs. My typical approach is to brake hard to get 5 mph below posted speed limit. Then let the brakes cool until speed gets to posted and brake hard again. This has worked well on many west coast mountain passes. Do I downshift, yes when posted speed is 35 mph or less. Always, safety first, do what you are comfortable with. And remember what commercial drivers are taught, speed kills. You can't go too slow down a steep hill.



Todd8

32' 2012 Itasca Suncruiser, w/ CR-V

So, your saying because the V10 doesn't have the ability to hold your rig back over 45 MPHs, you don't downshift at all ?

Why punish your brakes doing all of the work when a simple downshift will take much of the load off them. Maybe you will only need to brake hard 1/2 the time.

[Phil G.]

Originally Posted by Todd8

I've been driving a gasser for 23+ years. In the last 4 yrs have found that on 6% down grades the V10 gas engine does not have enough compression to offer effective braking at 45 mph. Our combined weight is about 21k lbs. My typical approach is to brake hard to get 5 mph below posted speed limit. Then let the brakes cool until speed gets to posted and brake hard again. This has worked well on many west coast mountain passes. Do I downshift, yes when posted speed is 35 mph or less. Always, safety first, do what you are comfortable with. And remember what commercial drivers are taught, speed kills. You can't go too slow down a steep hill.

Todd8
32' 2012 Itasca Suncruiser, w/ CR-V

I assume that instead you meant to say "...the V10 gas engine does not have enough compression to offer effective braking at 45 mph when trying to hold back your 21k lbs."?

The E450 V10 in our 11,800 lb. Class C holds it back just fine on all grades.

Of course the rear differential ratio that the V10 is spinning also has some effect on what the V10 can hold back on grades. A V10 in an E350 motorhome chassis with it's 4.12:1 ratio differential WILL NOT hold back as much weight on grades as will an E450's 4.56:1 ratio differential will on grades.

That's one of the reasons we bought a 24 ft. Class C and paid more due to it being on an E450 chassis instead of an E350 chassis.