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Old 05-20-2017, 11:56 AM   #1
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Driving Over Passes

Need some tips.

Next month I'm driving our new 38' diesel pusher on highway 80 over the Sierra pass. There are long 5-6% grades. I've read to leave my compression brake on and drop it to 3rd gear and just let ride at about 45 mph, and when breaking, stab the pedal vs riding the breaks.

Does that sound right to everyone? Looking for more tips. Thanks folks!!
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Old 05-20-2017, 12:00 PM   #2
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Seems about right, although you may have to use the up and down buttons to get the right gear to be in "equilibrium" and not need to stab the brakes, plus it depends on what gear the transmission is programmed to seek. My ISC with Allison 3000 in the '02 DSDP was programmed to preselect 2nd but it only had the exhaust brake. The present rig preselects 3rd but I have a 3 stage engine brake and very, very seldom do I need the "high" setting.
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Old 05-20-2017, 12:16 PM   #3
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If you want to be technical about it.......

You can calculate the maximum speed in any gear.
- Your engine manufacturer will give you the max rpm parameters, before it will upshift to protect the engine.
- Your transmission mfg will give you the gear ratios, I called mine and that took just a couple minutes
- Your chassis manufacturer will give you the rear end pumpkin ratio
- The tire mfg specs will give you the diameter of your tire, and you can verify by wrapping a string around.

A quick little spreadsheet then will give you the max mph for each gear, before it'll upshift. Then you'll know what speed you need to stay under, to enable your current gear selection to stick.

Your spreadsheet can easily do it for all 6 gears, but 3rd and 4th are really the ones you'll be focusing on. Also, calc it for 2000 rpm, and also your max engine rpm.

Then you can compare how your coach really performs, compared to your calculated values.

Although you may be running your genny and the house A/C going up the hill, you can also consider turning on your dash A/C coming down to strip off another 20 ish HP.

Definitely don't ride the brakes, if you start creeping up to getting close to the shift point, smooth hard braking to drop your speed back down and get off the brakes so they can cool. You don't want it to rise over the mph where it upshifts, because then you'll loose the engine/exhaust braking effect you had and have to slow it a lot with the service brakes to get the speed back down.

There are some mountain pass books you can purchase (east and west), which give you information about the grades so you can plan long before you get there. Search around though on the internet, wide variances in pricing.

Assuming you have a Cummins, if you google Cummins engine parameters, then find your engine, that'll give you some of the info that may be helpful.
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Old 05-20-2017, 12:23 PM   #4
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>"Next month I'm driving our new 38' diesel pusher on highway 80 over the Sierra pass. There are long 5-6% grades..."

Did that awhile ago, (5th wheel). Modern RAM diesel pickup with engine brake on... in the appropriate gear... you don't need to touch the brakes much at all.

I suspect your diesel will be the same way.
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Old 05-20-2017, 12:34 PM   #5
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When going down a hill, use the same gear that you used to get you up the hill.

Donner Pass (hwy 80) is not bad, long downgrades, yes; the biggest consideration is the amount of traffic- Trucks in the right lane will be plodding along at 15-20 mph on the uphill, then 60+ on the downhill. I stay out of the right lane on the uphill and just maintain my speed (45). On the downhill, just stay in your lane and let 'em pass (watch your right mirror for passing traffic).

80 east of Truckee has fewer lanes and some turns that may surprise you. Watch your speed as it may creep up on you, especially once you pass the (westbound) ag inspection station. Kinda curvy 'till you get to Bordertown.
In Reno, know where you are going (395 N or S) or 80 East and watch for merging traffic. You are bigger than most, but lotsa traffic. Stop at the exit for Fernley for fuel/food. Stop in Elko at the California Trail museum-fantastic!California Trail Interpretive Center | Elko, NV
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Old 05-20-2017, 03:54 PM   #6
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Go slow enough so your exhaust or engine brake will keep you at a steady speed. Use the brake to get you to that speed and then you should not have to use the brakes to keep your speed down.
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Old 05-20-2017, 05:46 PM   #7
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While I am totally new to RV'ing I'm a veteran at Donner. Don't worry about Donner Pass. It's really nothing too extreme. I drive a big rig over it all the time. Sun and snow. Nothing to be intimidated about.

The east to west is a gradual decline down the mountain that lasts for miles. The west to east direction is more of a drastic drop but still pretty mellow.

I assume your DP has a Jake Brake. "Compression brake".

I have never driven a dp motorhome however I assume it's similar to a rig.

There's all sorts of strategys to handle a mountain. Personally. I turn on the Jake. Grab a gear and see if it holds.

Seeing you're in Fairfield I assume you're heading towards Reno. Climb the long hill and up by Boreal you will reach the peak. There's a rest stop up there as well if you need a break.

Round the mountain. Turn on the Jake. Maybe drop a gear or so and see how it holds. Do you pick up speed quickly or slowly. Are you comfortable with the speed. If not. Brake a bit and go a gear lower. Again check how fast you're gaining speed and are you comfortable.

As for the breaking. Stab breaking is not necessary. Just don't ride the breaks and let them off and ride them again. Heat can become an issue but if your Jake braking and not barreling over or letting yourself get crazy it shouldn't be a problem.

The thoughts behind stab is that you are hard breaking for a short time and then letting off. Therefore it's less friction time on the brakes/rotors. However if you have your speed controlled by the Jake and gears you shouldn't have to brake hard or much to control your speed.

If it's your first time doing this then maybe work upwards instead of down. Meaning. Lowest gear and Jake and shift up to find the right gear/Jake/brake ratio for your setup.

Halfway down the hill it will turn kinda right and level out or go upwards a bit. This is a good time to just let it ride. No need to brake then it will start down again.

Don't get all psyched out. It's nothing. There's also no need to crawl down the hill at 35. You can safely navigate in the 50/55 area so long as you're comfortable with your speed gains.
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Old 05-20-2017, 06:12 PM   #8
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I believe the OP has a Cummins ISB 6.7-no compression brake, as I understand it, the engine brake is via a variable gate turbo (VGT). Don't know how this brake setup compares with a 2 or 3 stage compression (jake) brake.
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Old 05-20-2017, 10:06 PM   #9
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As a driving instructor for the Fire Department here in Sacramento we teach a lot in this subject. We instruct all our new drivers when on probation and continued instruction with veteran drivers. Knowing your engine rpm parameters is very key as stated above, remember the maximum amount of retarding power is at 90% of maximum rpm's. We teach a lot with vehicles that don't have compression engine brakes, so we emphasize the use of lower gears when necessary along with a braking tecnihue to help slow the vehicle while not over heating the brakes. It was stated to go down the hill in the gear you went up, well you can also use one less. This will start you down with higher rpm and slower speed, if it's too slow you can up shift as needed. we also teach a 5x5 braking technique. Let me explain: using max posted mph as your hit that speed you make a firm aggressive brake application and your looking for a 5 mph reduction over a 5 second application of the brakes. Then you let off and let the speed pick back up again to max and repeat as many times as needed. Good luck, we plan on that same route in sept when we return with our new Newmar Mountain Aire.
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Old 05-21-2017, 08:10 AM   #10
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Originally Posted by cruzbill View Post
When going down a hill, use the same gear that you used to get you up the hill.
I see this stated all the time, but really is not good advice, There many passes that are very steep on one side, but extremely steep on the other side. Besides, how many people with automatic transmissions even know what gear they were in going up?

A typical example is in the Bighorn range in Wyoming. Going westbound, up U.S. 14, I can do most of the climb in 4th gear, only occasionally dropping into 3rd.

Going down on U.S. 14A, I do most of the descent in 3rd, occasionally dropping down to 2nd.

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Old 05-21-2017, 09:02 AM   #11
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At 5-6% the exhaust brake maybe too much so you may need to turn it of and on with like third gear setting, when the brake is on the trans may shift to 2nd as it slows, then turn the brake off then back on as needed. On the climb get ahead of the hill by dropping to say 4th gear or 3rd as needed, only experience will tell. Also if you are slowed pick a gear to hold the motor to your best cooling RPM and just ride it out. Oh and look at the manual on your motor, on many the red line is above the the power red line with exhaust brake on. The trans is built to take care of itself so if you get out of safety parameters in will shift up. But as I say the 5-6% grades should not be a problem.

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Old 05-21-2017, 09:13 AM   #12
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A couple more thoughts:
- I don't get hung up on gear selection -- the computer coordinating the Cummins and Allison is much smarter about that than I am. When you flip on the engine (compression) or exhaust brake, whichever you have, it also automatically starts a downshifting algorithm, which I feel has a greater effect than the compression/exhaust braking itself.
- don't let your speed get over 55 or so; beyond that point your RPMs are getting too high to downshift.
- As stated above, don't ride your brakes, but Google "snub braking" vs. "stab braking" -- snub is really what you want.
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Old 05-21-2017, 09:27 AM   #13
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Originally Posted by MVP View Post
Need some tips.

Next month I'm driving our new 38' diesel pusher on highway 80 over the Sierra pass. There are long 5-6% grades. I've read to leave my compression brake on and drop it to 3rd gear and just let ride at about 45 mph, and when breaking, stab the pedal vs riding the breaks.

Does that sound right to everyone? Looking for more tips. Thanks folks!!
Went through the Grand Teton's last year. 10% grade up and down.

I NEVER shut off my compression break. Saves wear and tear on the service breaks. Most engine break restricted areas will never know it is in use because our coached don't rattle loudly from the exhaust when it engages.

Breaking is a learned art. You don't want to break hard. Ever. Apply the breaks just long enough to keep the speed down. Don't go much over 5mph above your desired speed before applying the breaks. Air breaks will loose pressure if applied too many times in a short distance. Steady, controlled breaking is the rule that works. Always be aware of overheating them. Pull over and stop if you suspect this is happening.

Downshifting is good to do but don't over tac the engine. Watch your gauges for over heating when going up hill. Down shift to increase RPM and to increase cooling.

Have a great trip.
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