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Old 07-07-2014, 11:14 PM   #1
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Driving Differences From Gas to Diesel

If our plans work out, sometimes thay actually do (but rarely in the timeframe intended) we will be selling/trading our gas MH in for a diesel powered coach - probably a Coummins 425 ISL.

I've heard that there is a difference in driving these two different engines - specifically up and down grades.

Anyone out there care to give us a preempted driving lesson?


1999 Winnie Adventurer 37.5' (we call it a 38' for short) with a Ford Triton V10
2009 Yorkie named Teddy
2010 Ausi named Bear
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Old 07-07-2014, 11:40 PM   #2
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Going from gas to diesel? A Cummins at that?

Set the cruise and let her eat. You'll be amazed at the effortless driving you're about to experience.

They're not the best engine brakes though. Your model might come with an exhaust brake or you can have one installed. If you don't have one just stay on top of your speed going down hills. Downshifted to where my max RPM is around 85% of the engine max I let mine get to the speed limit then use the brakes to pull it about 10-15 below the limit then off the brakes completely to let them cool off. Repeat as necessary. That cooling off period is important, most people just ride the brakes all the way down and lose them when they need them most.

Two things about diesel engines. 1. Don't fire it up and just drive away. Diesels fire off of heat within the cylinder, stone cold they don't have a lot of heat to work with and can have firing issues if worked too hard too quickly. Now, let me be clear, I'm not saying let it idle for an hour, but two to five minutes is all it needs. Plus it will take that long for the air pressure to come up.

2. Don't drop off the highway into the first restaurant you see and shut it off. The turbo needs a few minutes to cool off some and the oil running through it along with low load exhaust cools it off. If you have to drive a couple of minutes to stop then it will be fine, it doesn't need much time, just a little.

I was simply astounded when I switched to diesel power.

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2014 Sierra 346RETS
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Old 07-07-2014, 11:54 PM   #3
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Read up on air brakes & suspension systems there is a lot you need to know. Many states now require air brake training, and some companies will void insurance it you don't have the training you should , check local rules.

425HP, should cure any uphill, problems you think you might have , downhill , ISL, should have a true 2 stage engine brake. Cummins manual will cover the use of this feature. Most owners report the stage 2 is seldom necessary. Stage one provides all the downhill speed control they need. But depends on what you have on behind, trailer / toad.

Took me two hours on the highway to get used to , the change from , my Dodge V-10 with 10,000lb 5er, to my coach.
Safe travels .
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
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Old 07-08-2014, 01:20 AM   #4
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Just remember.....gas engines accelerate and diesels gain momentum.

Typically on a hill climb in a gasser, you wring it's neck, if you do that in a diesel, it will fall on it's face.
Don & Mary
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Old 07-08-2014, 11:36 AM   #5
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The difference is night and day.

Gasser, modest power, some struggle with any grade if loaded. Brakes are just enough with downshifting. Not the best for very long days on the road.

Diesel, much more power/torque, ride better, exhaust brake, comfortable, more capacities. Glad we upgraded.

2013 FleetWood Expedition 38B
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Old 07-08-2014, 01:40 PM   #6
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Air Brake Trainning ? never heard of that requirement in any state except perhaps Texas. If you are referring to CDL license then perhaps but I have never heard of any state requireing it for non CDL. If there is a list of states that require it please post it for others.
Don and Nancy
[2014 40QBH Phaeton, 2015 Buick Enclave, 2yr old sisters Sara n Kaycee, Havanese, Two Segways
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Old 07-08-2014, 02:04 PM   #7
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Originally Posted by djbmsu View Post
Air Brake Trainning ? never heard of that requirement in any state except perhaps Texas. If you are referring to CDL license then perhaps but I have never heard of any state requireing it for non CDL. If there is a list of states that require it please post it for others.
It's interesting that many states require an air brake endorsement for commercial drivers and school bus drivers, but not RVers. I got mine 40 years ago for a school bus license. Air brakes and suspension are enough different from autos and pick ups that an RV owner/driver should be educated if their RV is so equipped.

Driving a diesel is different than a gas powered vehicle. Torque comes at much lower RPM and it doesn't do any good to try to rev it to higher RPMS. I've had diesel autos for many years and anyone that tries to drive them has had to change behaviors to get it to behave.

The OP has made a big first step in recognizing there is a difference in gas and diesel vehicles. His learning curve will be accelerated by that recognition.

Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI
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Old 07-08-2014, 10:31 PM   #8
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Originally Posted by Dutch Star Don View Post
Just remember.....gas engines accelerate and diesels gain momentum.

Typically on a hill climb in a gasser, you wring it's neck, if you do that in a diesel, it will fall on it's face.

Yup, this about sums it up.

Oh, and by the way, the modern diesel motor will have either an exhaust brake or the engine brake which is better known as a "jake" . ither will get you down the hill safely, you just have to learn the limits of each and how to use them.

There is also the transmission retarder but the only coach other than bus conversions that has it is the Foretravel
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Old 07-08-2014, 10:45 PM   #9
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According to Allison

According to Allison the transmission in my Bounder has a transmission retarder that works in conjunction with the exhaust brake.

Going down grades is no longer terrifying like it was in our gasser. Going up grades is no longer a problem either.

Better suspension. Higher carrying capacity. Better fuel mileage. What 'a not to like?
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Old 07-09-2014, 04:01 PM   #10
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Recently, a couple of years ago, we changed our drivers licenses from NY to TX. Although we read about and answered some questions on air brake systems, on the road test the examiner did not put us through the air system departure check required for full CDL. In fact our backing test was from a straightaway stop back up in a straight line for 50 feet.

So we do NOT have an air brake endorsement even for a coach well over 26k lbs gvwr and it apparently is not required in TX either.

Paul Rocking down the road in our '12 Phaeton 36QSH, (in service May 2012 ) We tow an '11 4 dr Jeep Wrangler Unlimited Rubicon - Read my blog at http://xctraveler.blogspot.com/ AKA RVM86
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diesel, gas

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