Mountain Driving with the Allison Grade-Brake..

Have a question for those with the Allison transmission or a smilar one like the one on my Ford.

I was just reading the new edition of the Escapees Magazine. The article Mountain Driving, pages 24, 25 & 26. On Page 26 third column 3rd paragraph. They are discussing driving a Workhorse W22 gas chassis MH using the Grade-Brake feature of the Allison transmission. I didn't know what it was called. Huh... Learned something new. They wrote "Mike allowed the vehicle to run against engine compression with the engine speed varying between 4,000 rpm to 5,200 rpm depending on the grade. Each time we hit 5,200 rpm the transmission would force a shift to 3rd in order to protect the engine. Each time this happened Mike applied the brake for a few seconds to scrub off speed and this allowed the transmission to down shift to second gear again, allowing maximum engine breaking in the safe speed range".

Now one of the things they mentioned earlier is that they elected not to use the Grade Brake but preferred to manually shift down using the column shift.

Has anyone not used the Grade Brake and had it shift up? I have always used the Grade Brake. I thought that was what is was built to do.

When going down a grade that was about 8% I used the Grade Brake and hit the brakes only when needed to keep it down to a lower RPM and a speed that was safe.

I would enjoy to read your comments.

BC

TXBobcat said:

When going down a grade that was about 8% I used the Grade Brake and hit the brakes only when needed to keep it down to a lower RPM and a speed that was safe.

I would enjoy to read your comments.

BC

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Hello!

We tow the North Cascades often and I always use Tow Haul Mode (Grade Braking) Seems to work quite well although the first time it went to 6000rpm's I was a little surprised! When I am descending and need to add brakes, usually the tranny will downshift to a lower gear...higher rpms. I have never had it go the other way. We are headed to Twisp in the morning...over the mountains again! I will pay closer attention and report back!

Bobcat, we always use the Tow Haul for braking on grades but I think there's maybe a little confusion here. The gas chassis ( in that article) uses the 8.1 workhorse gas engine which has a much higher rpm range.

I don't recall exactly but on the Duramax I don't think I've ever seen it go over 3600 RPM on a downhill. I can tell you, I get really nervous cause it does go over red line on some of the downhills.

I don't know how true this is either, but I've been told, once you start braking on a downhill, don't remove your foot from the brake pedal. Always keep at least a little pressure on the brakes. I don't know the reason nor do I know if it's true. Just something I've heard in conversation.

Something I do, if I feel I'm going down at a safe/slow enough speed, I'll give er just enough throttle to upshift. If I feel I'm picking up too much speed again, I'll tap the brake to engage the grade brake feature.

We tow the North Cascades often and I always use Tow Haul Mode (Grade Braking) Seems to work quite well although the first time it went to 6000rpm's I was a little surprised! When I am descending and need to add brakes, usually the tranny will downshift to a lower gear...higher rpms. I have never had it go the other way. We are headed to Twisp in the morning...over the mountains again! I will pay closer attention and report back!

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SJH
Yes that is about what I experience. However I try to keep my RPM's less than 4,000 RPM's. Normally less than 3,500. I try to hit the brake enough to keep my speed within the needed speed if a lot of curves and RPM's below 3,500.

Do let me know how your do this morning.

I've been told, once you start braking on a downhill, don't remove your foot from the brake pedal. Always keep at least a little pressure on the brakes.

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Ray
Each of us has to do how we think is correct, but I have to say what you were told is incorrect. If you ride your brake your brakes especially the front brakes will get to hot. This will reduce your braking power and glaze your brake pads. You will have to apply even more brake pressure as you go down the mountain. This will continue until you have no brakes.

What I do is at the top of the hill (in Tow/Haul) hit the brakes to put the transmission in the Grade Brake mode and slow to a speed that is less than the posted speed shown. Then take my foot off the brake. When my speed increases to a point I want to reduce it, I press firmly until the speed I want to go is reached, then I let off. I would say apply the brakes for 5 sec then let off until you have to press again. You use enough pressure to drop speed quickly then let off. Never ride the brakes, they need a few seconds to cool. In fact if necessary have DW (or DH) apply the trailer brakes on the controller a little to give the TV brakes a bit longer to cool. This is only when absolutely necessary.

Remember when you apply the brakes initially your front brakes will make contact first. This is not what you want when going down a mountain. When you apply your brakes apply them with enough force to apply all 4 wheels. Your trailer brakes should work well during that time to slow the trailer.

Now I am not an expert, but I was raised in Wyoming and have driven the Rocky Mountains a lot when I lived there. Never had a problem yet.

However if any of you are in that area and want to go down a 10% grade to test your driving skills, drive down hwy 14A. I would suggest you leave your trailer at the campground.

This is what I do.
FWIW
BC

10-4 on the T/H mode and use grade brake. Do not ride your brakes ---

I use my tow/haul as much empty as I do towing going down the mountains. Works GREAT! The red line on the tach is "broken" until about 4600 rpms so I dont worry much until then.

I agree also.. I use the T/H in the mountains even when I am not towing the 5er. I sorta grin as the cars in front of me keep hitting the brakes.

I love the T/H.

BC

The newer GM Duramax's don't have the red line on the tach anymore (mine is an 08). I read over at diesel place that GM removed the red line because of confusion when grade braking. According to the discussion over there, the red line on the tach applied to acceleration only, not Allison induced grade braking. People were unnecessarily getting worried about red line RPM's when braking so the engineers decided to remove the red.

I was running some really high RPM's coming down an 8% off the Blue Ridge Parkway a couple of weeks ago. I trusted the computer and Allison and let it rev away. I only needed to touch the brakes at the switch backs. And since my tach is white all the way around, I had one less thing to worry about.

John

Ray LeTourneau said:

I don't know how true this is either, but I've been told, once you start braking on a downhill, don't remove your foot from the brake pedal. Always keep at least a little pressure on the brakes. I don't know the reason nor do I know if it's true. Just something I've heard in conversation.

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I suppose I shouldn't have really made this statement. As I said, it's something I heard. I do pretty much as everyone else has posted. Brake only as needed. In fact, if I know ahead of time, I slow down much sooner than the start of the downhill. That way, I rarely need to use the brake at all.

get a dodge then just set the cruse and forget it.

driver311

driver311 said:

get a dodge then just set the cruse and forget it. driver311

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Right !!!!!!!!! Phttttt !!!!!!!!!!!!

driver311 said:

get a dodge then just set the cruse and forget it.

driver311

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Your a funny guy! We have got to get together and have beer some time. That is if your still around.

We have owned several Duramax/Allisons and have always let the Allison do its job. The Allison is almost G.I. proof and many of you know what that means. The Allison will shift to what ever it needs, by that I mean it will not let the Duramax over rev in most situtations. The last Duramax/Allsion had whats called a paddle shifter were you can somewhat control the shifting but again the Allison will protect the Duramax..... The Freightliner we have now is the 3,000 series Allison which by pressing the mode button I can shift the Allison. However we have a two speed Pack brake system, similar to a engine brake/Jake brake. So I let the Pac Brake take care of the mountains. And we are in Colorado and there are some mountains out here, just today we were on Monarch Pass but it was only 11,312' at the Continental Divide but there are some 6 to 8 percent grades. Do love the two speed Pac Brake. I'm anxious to see how the Engine Brake works on the 2011 GM HD Trucks. No its not a good idea to ride any Type brakes, for sure not the new brake system (senior moment) can't think of the new type brake system. Let the Allison do its job, and it will take care of the Duramax. GBY............