We've tackled the hills of Big Bend.....

[Alpena Jeff]

Now moving west. I have some questions as I've never driven a vehicle this size in the mountains.

1) do I simply let the Allison do its thing? Or.....

2) do I utilize the single stage engine brake that the coach is equipped with?

3) do I manually downshift?

I know not to overwork the service brake.

Any advice is welcomed.

 

[Back2PA]

Generally speaking let the Allison do its thing, and use the exhaust brake to eliminate/decrease service brake use. The exhaust brake is most effective at higher RPMs so if yours doesn't automatically downshift when the exhaust brake is selected, then you'll want to downshift (mindful of max RPM). If the rig accelerates downhill during exhaust braking, use the service brakes before you get to max RPM, or the transmission will automatically upshift which can be disconcerting.


If you're finding you're using the service brakes a lot on steep downgrades, slow so you can use the next lowest gear.

 

[Larry N.]

Yes, use the engine brake. I leave mine on all the time, unless there's a specific reason to turn it off. However on the steeper downgrades (5% plus, especially) unless they are very short, you'll want to slow down a lot before starting downhill, since higher speeds will mean a LOT of service brake use. Under 40-45 is a good starting point, but keep it under 55 or it can soon get out of hand -- the steeper and longer, the slower. You'll want to experiment a little to find what works best for your coach and toad combination (your coach is 3 feet shorter than my 3709, so probably a little lighter).

 

[UTTransplant]

My Allison 3000 doesn?t downshift automatically when going down hills. I look at what gear it is in going uphill, then I downshift to that gear going downhill. Like Larry, make sure you aren?t going fast at the top of the hill. I leave my exhaust brake on all the time, but it still will go to 5 mph higher than the cruise is set before slowing down. Sometimes that is just too much, so I firmly brake until I am about 5 mph slower than I would like to be, then I gives me some time before it gets too fast again. If it happens too much, downshift some more.

 

[Larry N.]

I look at what gear it is in going uphill, then I downshift to that gear going downhill. Like Larry, make sure you aren?t going fast at the top of the hill. I leave my exhaust brake on all the time,

When my exhaust brake kicks in it puts the transmission selector in 2nd gear, so there's no need (or benefit, maybe not even ability) to downshift. But you bring up a good point about the brake not kicking in 'til 5 mph above the cruise setting -- mine's that way too, so I disengage the cruise control (if it's engaged) at the top of a steep hill, which means the brake kicks in immediately, and in any case I don't want it at the set speed during steep descents, especially the longer ones.

 

[jor_az]

I've only had one coach with a Jake brake and when engaged it downshifted the Allison 4060 to 4th gear. It worked great but I found the downshift from 6th to 4th to be too violent. I took the rig to an Allison shop and they changed it to an auto downshift to 5th. This gave me better control. I also had a Cummins shop change the Jake from a single speed (six cylinders) to a two speed (3 and 6). I found that these two modifications made a huge difference in downhill control. Both shops are in Coburg, Oregon just a block or so apart. Like others, I left my Jake engaged all the time except in slippery conditions. Once you get used to your auxiliary brake I think you will enjoy it and come to rely on it.
jor

 

[Larry N.]

The engine brake on my Ventana and on (the OP) Jeff's Ventana are not Jake brakes. They're VGT (exhaust) brakes.

A Jake brake is a compression release brake, built in to the engine itself. The VGT is variable geometry turbo, and is an exhaust brake. The VGT on my Ventana, though very helpful, is not nearly as effective as a 2-stage compression brake, though it comes close to matching the first stage that was on my Beaver, which WAS a compression brake. The Beaver downshifted to 4th when engaged, but the Ventana downshifts to 2nd.

HOWEVER, the downshifting I'm referring to is the SELECTION choice (left number on the Allison) -- the actual gear selected (right number on the Allison) doesn't get that low, on either coach, until the coach has slowed enough for the transmission to allow it without exceeding the engine's RPM specs (if it does that, it'll upshift).

 

[jor_az]

The engine brake on my Ventana and on (the OP) Jeff's Ventana are not Jake brakes. They're VGT (exhaust) brakes.

Ahhh... thanks for that clarification. Maybe my next coach (might have time for one more) will have a VGT!
jor

 

[AStravelers]

Now moving west. I have some questions as I've never driven a vehicle this size in the mountains.

1) do I simply let the Allison do its thing? Or.....

2) do I utilize the single stage engine brake that the coach is equipped with?

3) do I manually downshift?

I know not to overwork the service brake.

Any advice is welcomed.

Looking at the specs for the engine on the 2016 Newmar Ventana 3427 the max torque is at 1800RPM and max horsepower is at 2400RPM.

Going uphill you want to keep your RPM's in the 1800 to 2200 RPM range.  If you feel the engine under a pretty heavy load you want to manually down shift.  By heavy load, I mean "if you have to press the accelerator fairly hard to increase your speed by 1-3mph, then you are loading the engine and transmission which will cause overheating.  On a 7%-8% grade there is nothing wrong with going 35-45MPH in 3rd gear.  In a 10% grade second gear at 25 -30MPH may be best.  I have gone up 9-10% grades with sharp turns in 1st gear at 10-15mph, moving to 2nd gear as the road straightened out.  Bottom line keep your RPM's up so the engine and transmission are not laboring.  One of the gotchas, is a long 1-2% grade in warm to hot weather, especially with a 10mph head wind.  The transmission computer may not downshift to 5th and after a while the engine/transmission will get pretty hot. 

Going down hill.  There are usually signs showing the downhill grade.  If you have 7% grade engage the exhaust brake, slow down while it is still level, downshift from 6th to 4th or maybe even 3rd at 35-40mph maybe 45mp.  If your speed increases by 10-15mph in less than 45-60 seconds you may be going to fast and in too high a gear.  When you do manually brake, press hard enough to drop your speed by 10-15mph in 10 seconds or so and then get off the brakes for at least 45-60 seconds, 90-120 seconds is better.  BEST is just coasting for miles down the hill in whatever gear and speed allows you to not use the brakes at all.  That is not always possible, but it sure is relaxing to just coast for miles. 

 

[thelazyl]

I have my exhaust break on at all times.

When going down a hill, if I don't use the foot brake, the RV maintains speed via exhaust break resistance. There is no downshifting. There is no deceleration.

When doing the same down hill, but pressing the foot brake, the Allison will downshift and there is deceleration.

I am very much a novice in understanding this - I've been a DP owner for 6 months.

 

[AStravelers]

I have my exhaust break on at all times.

When going down a hill, if I don't use the foot brake, the RV maintains speed via exhaust break resistance. There is no downshifting. There is no deceleration.

When doing the same down hill, but pressing the foot brake, the Allison will downshift and there is deceleration.

I am very much a novice in understanding this - I've been a DP owner for 6 months.

As long as you don't need to manually brake more than every 60-90 seconds, to keep your speed from increasing more than 10-15 mph you are doing fine.  Repeatedly or continuously using your service brakes will over heat them and they may fade to the point you are not able to slow down. 

I don't know of an exhaust brake which will keep your speed down on a 4% grade.  1-2% maybe.

 

[Larry N.]

If you have 7% grade engage the exhaust brake, slow down while it is still level, downshift from 6th to 4th or maybe even 3rd at 35-40mph maybe 45mp.

As I wrote above, if the VGT brake (NOT a Jake or compression brake) is engaged, the 2016 Newmar Ventana (which Jeff and I both have) will select 2nd gear, meaning there is no need, and no ability, to downshift manually. You can do that manual downshift only if the VGT has not yet engaged.

Going uphill you want to keep your RPM's in the 1800 to 2200 RPM range.

Downshifting on the uphill run can sometimes make a difference. But it's all in the timing. On steeper grades, it will automatically downshift, but you can force it down manually a little earlier, thus keeping your speed up a little bit (given long and steep enough, it'll still get down to 30-40 mph, depending, but manual shifting can delay that a little). You're limited by the computer allowing only a little leeway -- it wants to protect the engine and transmission -- but that little can sometimes help a bit.

In the above, I'm speaking from the experience of many trips through the Rockies, on I-70 Denver to Grand Junction, through Rabbit Ears Pass, Berthoud pass, and many others, in both the Beaver I used to have and in the Ventana I now have, which is similar to Jeff's. There's a lot of steep up and down. That doesn't count all the other areas I've traveled in these two rigs. Other rigs may be different, but I know what these two do.

When going down a hill, if I don't use the foot brake, the RV maintains speed via exhaust break resistance. There is no downshifting. There is no deceleration.

I think if you check it you'll find that the gear selection is chosen as a downshift, but the downshift won't happen until you get the rig slowed. Also, on steeper hills, without the foot brake you'll accelerate unless you've slowed enough to let the exhaust brake work well, which happens much better at slower speeds.

 

[Alpena Jeff]

Wow! Lots of information here. To be honest, I'm a little nervous to reach my first steep downhill. I'm going to read through this several more times because that's what I need to do to make it stick!
If I'm understanding....keeping it simple, keep the engine break on, approach the crest at a slow enough speed to allow the engine break to assist. Don't overwork service breaks.
Still fuzzy on the manual downshift thing. I'll work on it.
Thanks all big time!
Oh, it's snowing in Deming NM. Recently arrived in 25+MPH winds. My heads tired.

 

[Larry N.]

Still fuzzy on the manual downshift thing. I'll work on it.

The manual downshift, is actually a manual gear selection (your choice, in other words), using the arrows, reading out on the left number, Jeff. The right hand number tells you what gear is actually in use. The computer actually changes the gears, trying to get to what you've selected, but not allowing speed/RPM/etc. to get our of hand and actually damage something, so if the right number is 5 and you change the left one to 5, nothing will happen, but if you change it to 4 or 3, the computer will make the change once you get slow enough that it sees no problem -- you can follow that by watching the right number.

The main confusion in the discussion in posts above is that the engine brake programming (from the factory, with Cummins and Allison combining to set the parameters) will automatically change the desired selection (left number) to 2 on the Ventana (different on some other coaches), thus you are unable to make any choices until the brake goes off, when the previous selection (whatever it was) is restored. With the brake off you may select whatever you want, but the VGT going on will override your selection until the brake releases.

Clear as mud?

 

[ArdraF]

Jeff, another great guideline is the signs for truckers.  If a sign indicates a lower truck speed, say 45 mph, on the next curve, then that's the maximum speed for you too.  The truck speed limits generally work pretty well for any large vehicle.

Also, every transmission downshifts or upshifts differently.  Ours seems to shift on the "5", e.g. 45, 55, 65.  This means if I'm trying to keep it around 50 mph then I don't let it get to 55 because I know it will increase in speed which I don't want on a downhill.  A lot of it is just trying it out to see what works at various speeds.  You'll feel better about it once you maneuver some steep grades.

ArdraF

 

[RedandSilver]

I'll give you one more opinion.

I DON'T keep the exhaust brake on all the time like some on here do.
I don't like the MH slowing down anytime I let off the accelerator pedal, which in my case if it were on - the MH couldn't coast.
Also in my case the exhaust brake only works when you don't have any pressure on either pedal.  IF the brake pedal is pushed
the exhaust brake disengages.

When I get to the top of a hill (or JUST before) I let off the accelerator pedal and switch on the exhaust brake.
The transmission shifts to 4th and IF it doesn't keep me to the speed I want then I will use the brakes to slow it down more then
let up and let the exhaust brake do it's thing again.  Most of the time it works well and keeps me at a safe speed.

I only drive 55-58mph most of the time - so your results may vary.

Don't over think this issue - it's not Rocket Science.
You'll be fine.

 

[AStravelers]

Wow! Lots of information here. To be honest, I'm a little nervous to reach my first steep downhill. I'm going to read through this several more times because that's what I need to do to make it stick!
If I'm understanding....keeping it simple, keep the engine break on, approach the crest at a slow enough speed to allow the engine break to assist. Don't overwork service breaks.
Still fuzzy on the manual downshift thing. I'll work on it.
Thanks all big time!
Oh, it's snowing in Deming NM. Recently arrived in 25+MPH winds. My heads tired.

A little nervous is fine, it means you are going to be cautious.  Experience with the downshifting, exhaust brakes and service brakes will come with usage. 

I guess since you have a Ventura you may be limited with the manual downshifting since the exhaust brake tells the computer to automatically "request" but not force 2nd gear.  When RPM's go low enough it will downshift to a lower gear (that is when you are going down hill and your speed is increasing with your foot off of the accelerator).

As others have written, the computer won't let the transmission down shift until the RPM's are low enough so that the downshift won't result in the engine exceeding max RPM's.

Two key things:
--  Down hill, keep your speed down and use the engine braking (exhaust braking) to keep your speed down so you can use your service brakes a little as possible.  You can gain some experience when you come upon a 4% or 5% grade on an interstate or nice wide highway.  You will probably be at hwy speed of 55-60mph, so turn on the exhaust brake and if that doesn't start slowing you down, manually downshift from 6 to 5.  Work towards a goal of going down the hill w/o using the service brakes or using them very little.
--  Up hill, don't let the engine work too hard.  Down shift to keep your RPM's up. The downshift can be as simple as just pressing a little harder on the accelerator, or if it upshifts and drops your RPM's under 1800 and then you have to press the accelerator to downshift and get your RPM's back up, just manually downshift and use the accelerator to keep your speed and RPM's pretty constant.  Just like down hill you can practice this on any fairly mild uphill climb of 4-5%. 

 

[Larry N.]

You will probably be at hwy speed of 55-60mph, so turn on the exhaust brake and if that doesn't start slowing you down, manually downshift from 6 to 5.

Al, with the brake on he can't do that (it's already at 2nd gear). With it off, the downshift will have minimal effect, less than with the brake on. Uphill, of course is different, since the VGT isn't involved.

 

[AStravelers]

Al, with the brake on he can't do that (it's already at 2nd gear). With it off, the downshift will have minimal effect, less than with the brake on. Uphill, of course is different, since the VGT isn't involved.

That is why I added the 2nd paragraph:

I guess since you have a Ventura you may be limited with the manual downshifting since the exhaust brake tells the computer to automatically "request" but not force 2nd gear.  When RPM's go low enough it will downshift to a lower gear (that is when you are going down hill and your speed is increasing with your foot off of the accelerator).

Anyways the bottom line is to do what you have to do to keep your speed down and let the engine braking and exhaust braking do the work to slow you down as much as possible. 

With the VGT I guess you press on the brake to slow you enough to get the computer to downshift and then figure how to keep it from upshifting, if possible.  I would think it just takes using the VGT and working with the computer to figure out how to get it to do what you want it to do.  That is slow you enough to keep your foot off of the brake as much as possible.

Computer are wonderful, but there are times when there should be a way to tell it to let a human override the computer. 

 

[Neal]

I fall in the same camp as RedandSilver. Also don't care for the switch beside me and having to take my hand off the steering wheel to turn it on. So, I installed a foot pedal, located similar to a clutch location, and engage it with my left foot as needed.