Mountain driving

[lenny-shawna]

Hi All,
We are planning an out west trip this year which will include extensive mountain driving. Yellowstone, Tetons, Glacier are just a few of our planned visits.

My main concern is weather to manually shift the Allison or let her do as she wishes. I do know to use the exhaust break, go down the mountain no faster than I went up and to pump the breaks as opposed to riding them to help keep them cool.

Most of my research indicates to let the transmission decide.

So all you experienced mountaineers I would love to hear your input.

On a side note, any suggestions or must sees would be appreciated. Lastly, should I bring a dehumidifier? I was in NC over the summer and had a tremendous amount of moisture in the coach and do not want a repeat of that.

thank you in advance!

[wolfe10]

Correct.

Exhaust brakes are either ON or OFF.

Engine compression brakes are often offered with a HIGH (all 6 cylinders) and LOW (3 cylinders)doing the "braking".

[Mile_High]

The exhaust brake on that tour will do you well! You should have the hi/lo on that (mine is only one setting).

Once that Allison reaches a certain speed over the gear you are trying to downshift into, it won't do anything. At that point you have to brake down slow enough for it to downshift. Kind of a pain. Better bet is when you crown the hill, pick a conservative gear while you are going slow - you can always upshift.

ON EDIT - I have been "privately" corrected that there is no such thing as a hi-lo exhaust brake, so pardon my ignorance - its whatever you push that says Engine Brake and has a Hi-Lo on it. Comes on every 450 Freightliner I've ever driven. :R

[RayChez]

You shouldn't have any problems. Use your Pac-brake going down all grades and if it is still picking up speed, just tap on the brake pedal for a couple of seconds. Do not ride the brakes going down hill.

I just got back from Yosemite, Ca and it was a piece of cake. Been to Yellowstone many times and I do not remember any steep grades, unless you come down through Cody, Wy. I believe it is highway 14 which is very steep according to posts I have read. I usually come down from the north coming from Montana, or the west coming from California and it is not bad at all.

[tinkerer]

It depends on traffic condition also. Generally a loaded semi is a little slower than my coach, so if there is a quite a bit of traffic I don't like changing lanes often so there are times I tuck in behind a truck and shift manually keeping the rpms up so it doesn't begin to overheat from low rpms. This might not be true for all coaches though.

[lenny-shawna]

Thank you everybody, I really appreciate all the valuable insight you shared with us.

[Kayteg1]

Bikeboy57 wrote:
There have been some good comments.

Let me add two things.

One, I find that if I take the mountain curves 5 or 10 mph less than the posted sign that my co pilot is much happier.

Two, keep an eye on your engine temp when climbing long grades. If you think it is starting to rise much above normal, then force the transmission into the next lowest gear. The higher RPM will increase the fan speed and pump more air through the engine, both help with cooling.

Not only more air, but going slower, you will use less HP / minute, meaning the engine will generate less heat.
Not too many vehicles have cooling system design to drive with gas pedal on the floor for long minutes. Some diesels can do it but this is one of the common misconceptions.

[JoeH]

Since you have a Freightliner, set up your light bar display to show engine temp and tranny temp so you can monitor them. When climbing hills out there, I found that I had to manually downshift to keep the engine coolant temp from getting to hot. That was only a couple pretty severe roads most of the time the engine/tranny knew where to be.

We spent a few months out there last summer and really liked the national parks in Utah. From there we headed up to Yellowstone and the Grand Tetons.

[Bikeboy57]

There have been some good comments.

Let me add two things.

One, I find that if I take the mountain curves 5 or 10 mph less than the posted sign that my co pilot is much happier.

Two, keep an eye on your engine temp when climbing long grades. If you think it is starting to rise much above normal, then force the transmission into the next lowest gear. The higher RPM will increase the fan speed and pump more air through the engine, both help with cooling.

[RedRocket204]

Only one person slightly eluded to this so wanted to bring it up...

Sounds like you possibly have no experience driving the mountains out west and that is fine and is good you are asking. There has been good information mentioned in the responses but also, please make sure you are being considerate by using right lanes and turnouts when you are the slower vehicle on the road. Many mountainous roads have limited amounts of lanes and it is considered a good driving habit to be aware of others on the road, being considerate in the process using right lanes/turnouts.

Thanks and enjoy your trip!

[eubank]

You know, mountain driving is more than just uphill and downhill. It means curves, lots of them, requiring you to slow down even more than during straighter stretches. Often enough, it's a hairpin that will require you to be at less than half of your speed in straight stretches.

Under those common circumstances here in the west, I always downshift and keep it slow. Remember this: If you're going at a good speed now, you won't be for long because you'll be too fast for the curve ahead of you.


Lynn

[nevadanick]

The Allison will downshift itself when the ex brake is activated. Also dont pump the brakes as you will deplete the air supply. The proper way is to apply steady pressure to the brake pedal until you have slowed to your target speed and then let off the brakes. Here is an example of how i drive and i drive mountain roads alot. If the hill is fairly steep and long i start the downhill at 45mph and when my speed reaches 50 i then brake back to 45 and let off the brake, repeat at 50. Also your ex brake is most effctive at high rpm like in the 2500 rpm range depending on what engine you have. ISB will be a little higher than ISL. you cannot hurt the engine as it will upshift when it reaches to high of rpm of which should not happen once you learn how it works. I just seen that you have a 450 hp ISL, it should have a 2 stage compression brake instead of an ex brake.

[Ivylog]

If I can see that it's a fairly straight uphill/downhill I'll let the tranny do it's own thing. If not then I'll manually down shift so when I touch the throttle after slowing for a curve to speed up a little it will not up shift.
When I know it's going to be a long climb I'll down shift early to get the RPMs up for better cooling and leave it in the same gear going down.

[J-Rooster]

If you feel that you are braking too much going down hill, then manually shift down one gear and see how that goes! If that works then your where you want to be on a downgrade. If not and your on a extremely steep downgrade (like Chinook Pass in Washington State, West Side of pass) drop two gears manually. On I-90 highway speeds with the Jake On and slight braking should do the trick for you. I've drove diesels (semi's) my whole adult life (44-1/4 years) just so you know who is giving you this advice. And on your dehumidifier I take mine everywhere I travel especially in the Northern Tier States where your going. Good Luck in your travels.

[ORbiker]

As I come over the crown of the large slope crawling along at 30 or 40, I just ease on down. The less speed you start will going down, the better.

I like to let any cars that are following go on when ever possible.

Safe travel and enjoy the west.KEN