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Old 02-09-2016, 01:58 PM   #1
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Downshift or exhaust brake

We just purchased a 06 revolution LE and when we go to pick up next month we will be going up and down some grades. Nothing to long like the smokies, and I was wondering as I am decending should I use a lower gear or us the exhaust brake or both.

Thanks
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Old 02-09-2016, 02:05 PM   #2
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The exhaust brake will downshift the transmision on it's own.
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Old 02-09-2016, 02:11 PM   #3
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Depending on the power of the braking of your exhaust brake. I would recommend exhaust brake first then down shift if you continue to build up speed. We have never met a grade that our engine break did not give us enough braking power without down shifting, and we have been through the Rockies and Sierras with very steep long grades.

If your exhaust brake does not offer enough slowing power here is a note to consider I learned in my commercial driving school; you should go down in the same gear you went up with. Also make sure your speed is slow going over the crest and keep your speed low going down. The biggest mistake you can make is building up too much speed then try to pull it back.

Familiarize yourself with stab braking and controlled braking. This will help if things get out of control.

Stuart
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Old 02-09-2016, 03:56 PM   #4
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I used the exhaust brake as much as possible. When I engage it the transmission will go to 4th gear if the speed isn't too high. If I start building speed I will pulse the service brakes to slow down. I avoid riding the brakes as they can overheat and the shoes can glaze over.
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Old 02-09-2016, 04:01 PM   #5
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Originally Posted by S-n-L View Post
Depending on the power of the braking of your exhaust brake. I would recommend exhaust brake first then down shift if you continue to build up speed. We have never met a grade that our engine break did not give us enough braking power without down shifting, and we have been through the Rockies and Sierras with very steep long grades.

If your exhaust brake does not offer enough slowing power here is a note to consider I learned in my commercial driving school; you should go down in the same gear you went up with. Also make sure your speed is slow going over the crest and keep your speed low going down. The biggest mistake you can make is building up too much speed then try to pull it back.

Familiarize yourself with stab braking and controlled braking. This will help if things get out of control.

Stuart
I have to ask what this is??
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Old 02-09-2016, 04:13 PM   #6
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I have to ask what this is??
My guess is that it is the same as Stomping on the brake to reduce the speed 5-10 mph quickly before letting off of the brake pedal.

With my total weight, coach and trailer, I do that often when descending a steep grade with the PRXB PacBrake.

Dr4Film ----- Richard
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Old 02-09-2016, 04:19 PM   #7
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"Travelwrench".....Is this your first coach with an exhaust brake?

When you pick up your new coach, the exhaust brake will be set up to try and downshift, while the exhaust brake is working, to either 4th gear or 2nd gear. Which one it selects is something that was set by the manufacturer of your coach, but can be changed. It's a preference issue.

If you have the exhaust brake on and it's not sufficiently slowing you, you won't be able to downshift to another gear. The Allison will not allow the engine to over rev and down shift. If you're not slowing down, you'll have to use the foot brakes, get the speed and rpm down so that the transmission can downshift.

My last coach was light with a 400 ISL. I could climb just about any grade out west at 55 mph while towing my Silverado. Even though I could do that, I my exhaust brake wasn't powerful enough to hold me at 55 mph going down the other side or a grade that was 6% or steeper.

Every coach is different depending on the rear end ratio, tire size, engine size, weight and if you're towing. So what works for some may not work for others. I found on my previous coach that if I wanted to use just my exhaust brake and not my foot brakes, I would have to start down the 6% grades and steeper at about 43 mph, where the Allison dropped into 3rd, in order to hold my speed. The problem is that you have cars and trucks rushing up behind you. You either have to not worry about them or pick up your speed and apply your foot brakes every so often. This can be done on short grades, but can get dangerous on long ones, by overheating your brakes.

So.....your coach wasn't really designed to just downshift, but was designed for the Allison, in concert with the exhaust brake, to slow your coach. You'll need to see how effective the exhaust brake on your new coach will be. Remember, once the coach picks up speed, you CAN'T downshift at will, the Allison won't allow it.

As you start to drive the coach over the same roads near you, you'll learn what your exhaust brake is capable of. As you venture out farther, you'll have an idea of what you need to do to control your speed. Experiment and see what works best.
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Old 02-09-2016, 04:25 PM   #8
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Learn at what RPM the transmission will up shift with the exhaust brake on.
Then you will know when to stab the brakes before that RPM is reached.

On my ISB it is 3,200 with the Allison 3000 6 speed. I stab at 2,900-3,000
Higher RPM give more braking HP.
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Old 02-09-2016, 04:47 PM   #9
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Just DON'T let the coach pick up too much speed so that you have to ride the brakes to slow it down! You'll end up burning up your brakes really quick!

Start down the grade SLOW and when you start to pick up speed, press the brake pedal HARD for a few seconds, then release. Keep doing this until you get it back down to the speed you want to maintain. The exhaust brake is not going to do it's job if your speed is too fast!
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Old 02-09-2016, 05:44 PM   #10
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Quote:
Originally Posted by Dutch Star Don View Post
"Travelwrench".....Is this your first coach with an exhaust brake?

When you pick up your new coach, the exhaust brake will be set up to try and downshift, while the exhaust brake is working, to either 4th gear or 2nd gear. Which one it selects is something that was set by the manufacturer of your coach, but can be changed. It's a preference issue.

If you have the exhaust brake on and it's not sufficiently slowing you, you won't be able to downshift to another gear. The Allison will not allow the engine to over rev and down shift. If you're not slowing down, you'll have to use the foot brakes, get the speed and rpm down so that the transmission can downshift.

My last coach was light with a 400 ISL. I could climb just about any grade out west at 55 mph while towing my Silverado. Even though I could do that, I my exhaust brake wasn't powerful enough to hold me at 55 mph going down the other side or a grade that was 6% or steeper.

Every coach is different depending on the rear end ratio, tire size, engine size, weight and if you're towing. So what works for some may not work for others. I found on my previous coach that if I wanted to use just my exhaust brake and not my foot brakes, I would have to start down the 6% grades and steeper at about 43 mph, where the Allison dropped into 3rd, in order to hold my speed. The problem is that you have cars and trucks rushing up behind you. You either have to not worry about them or pick up your speed and apply your foot brakes every so often. This can be done on short grades, but can get dangerous on long ones, by overheating your brakes.

So.....your coach wasn't really designed to just downshift, but was designed for the Allison, in concert with the exhaust brake, to slow your coach. You'll need to see how effective the exhaust brake on your new coach will be. Remember, once the coach picks up speed, you CAN'T downshift at will, the Allison won't allow it.

As you start to drive the coach over the same roads near you, you'll learn what your exhaust brake is capable of. As you venture out farther, you'll have an idea of what you need to do to control your speed. Experiment and see what works best.
Don,
OUTSTANDING ANSWER! So many just blurt out an answer without any form of explanation, especially to someone who may be new at the game. While we can't teach new drivers of D/P coaches, and their intricacies on a computer, we can advise, with at least some form of detail so a potential owner can get a clearer idea of what's what.

OP,
As has been somewhat explained, the E/B will work, if and when "called for" by meeting certain conditions. First, you must be above a certain MPH in order for it to work. I.e. it won't work below I think, about 3 mph.
Second, your engine "ECM" or, engine control module, (the brain that contolls all engine functions) is the master control of the E/B based on again, what's been stated but, in simple terms, your foot must be completely off the throttle pedal and, in some cases (maybe most) your CRUISE CONTROL must not be in the SET mode.

That is, if your cruise is in the SET mode, as in, it's driving the coach, not you, and you start to descend a grade, your coach will simply automatically pick up speed, even if your E/B switch is in the ON position. In that case, you have two remedies. (1) Tap on the brake pedal to disengage the SET mode on the cruise or, (2), if you have a Smart Wheel (Smart Steering wheel option installed in the coach), you can reach over and hit the CANCEL button on the cruise set of buttons.

Either of those will disengage the cruise and, therefore will allow all set perameters for E/B operation, to take place. Now, once the E/B is working, as has been stated, it will slow you down, based on Dons explanation of the set of driving conditions. Obviously, if the grade you're descending on is too steep or, the particular time you asked for the E/B, was too late for the E/B to do all the work, then a bit of application of your regular brakes, TO ASSIST THE EXHAUST BRAKE for a short term, to get the coach to a slowed speed, that the E/B can handle keeping it at a speed you're happy with.

And, also has been explained, the Allison Tranny "TCM" or, Transmission Control Module will work in conjunction with the Engine ECM, to keep both the engine RPMs and transmission protection components working together so that things are not getting out of control, as in too many RPMs while descending.

And, in about oh, 95% of these Allison shift pads out there, (unless they've been modified or re-programmed), the second the E/B goes into action, it (the shift pad) will show what's called a "Target" gear. And, about 95% of the time, that target gear is 2nd gear. Some unknowing new drivers, think that when they see that, that even though they're traveling at 65 mph and begin E/B operations, that the tranny IMMEDIATELY DOWNSHIFTED TO SECOND GEAR!!! Well, if that were the case, most of those Allison parts would be spread between two or three zip codes.

So, what you'll see, is what the transmission, is AIMING FOR, not what it's presently in. Hope this helps some.
Scott
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Old 02-09-2016, 06:40 PM   #11
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Don, I have been fortunate enough to find this forum and you are a great contributor. Thank You for all of your responses and taking your time to explain to folks not so knowledgable.
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Old 02-09-2016, 07:18 PM   #12
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Hello All,
Just an added note here in what works good for me in addition to what's already been said........I've spent a good deal of time driving steep Tennessee grades, and what I've done is.....at or near the top of a grade, based on posted length and percentage of grade, choose my target downhill top speed say (for an example) 45 mph. But as I start to head down, set my cruise at 40 mph, and sometimes select a lower gear range (usually 5) on my Allison.... I have my engine brake switched on high setting. Now, as I pick up speed, when I reach 5 mph over my active cruise setting, the engine brake then engages. It does a great job holding me at that predetermined target speed, and I just calmly motor down the grade. It keeps the engine at a comfortable rpm also, usually around 1800 or not much more. Of course I keep and eye on things, pay attention, (pause loud radio and jibber jabber with passengers), and I keep the foot ready to pulse the service brakes to assist if needed. But I've had to do that very little, except maybe to prepare for a curve in the grade etc.

Out West in the Rockies and the like this plan may not apply, not sure. But like Don said, safely and very carefully experiment a little. It's just getting to be "one" with your machine and it's own nuances and find the sweet spot performance wise.

Wishing all safe travels,
W.D.
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Old 02-09-2016, 07:18 PM   #13
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We actually drive with the engine brake on all the time...

Some don't like it and would rather turn it on as needed, because it will downshift TOO often if the throttle is feathered,

but MOST of the time I am on Cruise control so it doesn't need to downshift unless I turn the cruise off and/or slow down..

But the good thing (in MY humble opinion) is that since the exhaust brake is already on I don't have to 'find' it if I have to stop quickly, it REALLY does a great job of slowing all 65 foot of rv and toad
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Old 02-09-2016, 08:00 PM   #14
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travelwrench - nice ride
Chances are your MH has and Engine brake not an exhaust brake. also 1200+ pounds of torque should give you a substantial breaking effort as well as a great ride going up the rolly polly hills.. Many people have given you good advice about keeping your speed down at the top of hill because it is hard to stop or even slow all that weight when descending a steep grade. Stabbing or pulsing your brakes is good advice, to avoid over heating the brakes. A few second of hard braking is better than riding the brake. hot brakes won't slow you down.

I have come to some extremely steep grades but that is because I like to travel back road and even dirt roads. I like to see the real county roads. (my favorite song of John Denver RIP). When I get to these type of roads I slow down real good and have even pushed the ONE button on my Allison to safely guide me down the slope. yEA - THAT IS SLOW !

so the answer to your question is yes and yes. Normally your automatic electronic management systems will keep you slowing down when that is what you want but you can override the system on REALLY REALLY STEEP HILLS BY stopping at the top and down shifting into 1st gear. The Allison trans will not automatically shift to 1st gear when automatically down shifting, it stops down shifting to the target gear as described above which is 2nd. when the speed drops to a point below second gear cut off it will release the engine brake to an effect of coasting. at least that is way mine works. try yours out on some back roads and see how it works. Once use to the action you will know what to expect. good travels.
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