steep grades

Hi,

You can get a GPS program by DeLorme Topo 10.0 (or maybe 11 is out now?) that you can plan a trip, then click to get the elevation changes along the route. It will give maximum grades up or downgrades. It is simple to change a route, and check the elevations of the new proposed route, and adjust your travels as desired..

However I still wonder why the worry about the grades? I know I avoided some just to save gas, but others worry because of fears of speeding down the hills out of control. Yet that is easy to take care of with proper equipment, and slowing down and downshifting to 2 gear if required.

I have been up and down highway 120 into Yosemite from highway 395. The "Pass" is around 9,500 feet elevation, while highway 120 / 395 interchange is closer to 2,500' elevation. There is a long 6% or 7% grade in between, and we decided to unhitch our tow car (Honda CRV) while going back to 395 to avoid to much heat on the brakes. By going slow, and shifting to 2 gear, we slowed the RV to around 35 - 45 MPH while using minimal amount of braking while driving.

The car came down the hill without any problems. By going slower, you give the brake disks time to cool off. If driving say 55 MPH, then you are going down the 1 mile grade in only about 1 minute, while at 40 MPH you will take about 75 seconds. That extra 15 seconds will allow the brakes to run cooler.

On one especially steep grade, from highway 395 up to Sherman Pass (11,500' elevation) I stopped about 1/2 way down the hill, and got out and took some pictures. That gave the brakes another 5-8 minutes to cool off before continuing.

Keeping the motorhome in 2 gear (out of 3 in that case) only allowed the RV to reach about 45 before reaching the maximum RPM near 3,800 RPM, and then apply a little braking pressure before letting them cool a bit, and keep going. While moving at 45 MPH, the air is going about 75 feet per second across the brake shoes and disk brake pads.

Leaving the RV or even your personal car in overdrive while going down a hill means that you will have to ride the brakes. It is so easy to shift down one gear or two, as needed to let the engine provide much of the braking, without needing to overheat the service brakes or disks.

Fred.

Viola is in the SW corner of Wisconsin, right? The hilly 'driftless' part of the state? Practice driving in and out of the valleys around home, and you should be fine on any major highway out west. I90 heading west out of the Mississippi river valley will be as steep as anything you'll encounter in Montana.

if you stay in the interstates the grade will be no more than 7%. federal law.

Hi. Welcome to site! Staying on the highways as much as possible is good advice. I think most max out between 5-7% max. I'm no tranny expert but I've always understood that most heat builds up in a transmission when it continually "hunts" up and down for the proper gear. Try to avoid this as much as you can by picking a gear like 2nd for example and leaving it in that gear while going up a long grade. Watch your RPM and you can stay in that peak powerband usually between 3000-3500. On the really steep grades don't be afraid to maximize 1st gear for a long stretch if needed just keep it below your redline. Avoid the "hunting" and you should be fine. If you don't already have a separate transmission cooler, you may want to put one on. Good luck!

Transmission heat will be your main concern. There are a lot of posts on this and other forums about it. You need to understand how the torque converter works and when it locks in. On my Dodge Cummins if I am in tow haul mode with the shift selector in 2 and keep it above 28 mph the torque converter stays locked and I can pull any grade for any length of time without building heat in the transmission. As soon as the torque converter unlocks the heat starts to build fast. Extended periods of temps above 250 will deteoriate the transmission fluid. Learn how your transmission works and how to keep the heat down.

smkettner wrote:
Stay on the boring interstates and you will be fine for the first couple runs.
It is fine to slow a bit on the up and preferred to slow a bit more on the decent.
Don't ride the brakes. Let it coast up some then moderate speed down 10 to 20 mph and repeat. Brake before a curve.
Have fun :B

I just use the gears to hold back the truck, and trailer. All the way down to first if needed. I can come down most any grade with out using the brake hardly at all. Just for the sharper curves.

Stay on the boring interstates and you will be fine for the first couple runs.
It is fine to slow a bit on the up and preferred to slow a bit more on the decent.
Don't ride the brakes. Let it coast up some then moderate speed down 10 to 20 mph and repeat. Brake before a curve.
Have fun :B

Is there a reason to shy away from grades?

All depends on your tow vehicle...