Gas vs Diesel (I've read the FAQs!!)

[ZagiFlyer]

Hello to All,

We *still* have the Thor Jazz in my sig, and it's still a going concern, but the wife is up for a change and "we" are wondering if a Class A would fit the bill. Many of our trips are long-range and we'd like to be comfortable driving cross-country -- my daughter has informed me that the back seat of an extended cab is not making her back happy on 6, 8, 12 hour drives.

Keeping in mind that we're coming from a 5th-wheel towed by a 6.0L gasser, my wife is under the impression that a DP will fly up the Grapevine (6% grade) at 50-60 mph. Is this true? I wouldn't expect it, since the HP/torque required to move 26,000 lb up a 6% grade at 50 mph would be enormous.

I've read the FAQs and searched the forums, but I didn't find anything specific enough so here is my question:

Thinking along lines of the Grapevine or other steep/long grades:

• At what speed are you 36-40 ft. DPs getting up steeper grades
• At what speeds are you 36 ft. gas Class A's getting up steeper grades?

For comparison, my rig gets us up the Grapevine at about 35 mph, but it's struggling mightily at 4400 RPM.

I need to set her expectations realistically if I am to acquire any semblance of domestic tranquility when we upgrade.

Thanks!

[OhhWell]

If you think that high RPMs means struggling, you will not be happy with a gas motorhome. The DPs that really chug on a grade are usually the older ones with sub 300hp powerplants.

I have no idea what your current setup weighs in at but a guess might be about 17,000 lbs fully loaded for camping. Were you full throttle at 4400 RPM and the chevy could only get you 35 mph?

Your style of RVing definitely sounds like you would be MUCH happier in a class A. If you go gas, make sure you get a newer v10 with 362HP if you want some speed on a 6% grade. I have a 37' Gasser that weighs 18,000 lbs empty with the oldest Ford v10 but with a Banks kit that is supposed to get me to about 300-310 HP. Where we live, the toughest grade I have had to conquer is 4% so I really can't give you real world speed for what you will be doing.

Just buy one that you love and take your time on the hills!

[Tom_Barb]

We weigh 27,000 empty, we travel at 28,500 (+-) and can pull most any grade at the speed limit, we topped the continental divide on I-90 this trip at 55 MPH. We run a cummins 8.3 with a 400 horse programmer, Allision 6 speed. banks intake system. This trip 3500 miles so far, has averaged 9.97 MPG set the cruise at 60-65, transmission to economy, and let the computer drive the coach.

[rgatijnet1]

Exactly how much time do you think you will spend on steep inclines? We travel out West all of the time and the actual time that we spend on steep inclines is so minimal, compared to the thousands of miles that we travel, that I would never use it to determine which coach I would buy. All coaches will make it up the hill, and all engines will outlast the house portion of the coach.
The floor plan is still the most important thing and you will spend more time living in your coach while parked, then you will driving it.

[Bruce_Brown]

TucsonJim wrote:
Not a Class A Response, but here is my before and after:

Before

2004 Chevrolet 2500HD extended cab 4x4 6.0L Gas
2007 Keystone Cougar FW (Approx 9800#)
Speed on 6% grade - 35-40mph.

After

2013 Ford F350 Crew Cab, 4x4 6.7L Diesel
2014 Grand Design Reflection (Approx 12,900#)
Speed on 6% grade - 60-65mph with more pedal if I needed it!

Granted, the Chevy was 10 years older, and only had the 4 speed transmission. You can stay with a fifth wheel if desired and have all the power you need. But I'm guessing that if you want a MH, you'll see similar results in the power plants.

I 100% agree. The OP doesn't have a HP problem, he has a torque problem.

I might be able to offer a different perspective as we have both a DP and a Super Duty diesel w/ a TT. (Thats another story...)

Not the Grape Vine, but Rt 26 out of Johnson City, Tn;

2000 V10 gasser MH - brought to it's knees, 30 MPH tops
2003 DP w/ Cat 3126, 330HP/860 TQ - 55 MPH
We've never done that trip with our current MH (2008 DP, 400HP/1200TQ), but the power difference between the '03 and '08 is amazing. The '08 makes the '03 look a little weak.

A few years back we did the Yellowstone trip with our current MH, The Rockies didn't even make that one breathe hard.

With the TT, last year we did a Colorado Elk hunt; 5 guys with gear pulling a 33' Bunkhouse TT - '13 Super Duty Crew Cab, 8' box, pulling around 10,000#. The run from Cheyenne to Laramie Wy is a pretty long, steep pull. With the cruise set at 70 MPH the speedo never dropped below 69 MPH.

My suggestion to the OP - if you're otherwise happy with your fiver I'd suggest you take a good hard look at a new Super Duty Crew Cab w/ the 6.7 diesel. As mentioned, the Colorado trip was 5 grown men riding for 31 straight hours and we were all comfortable - and for the record I traded in an extended cab on the Crew Cab - night and day difference in the comfort level.

If you're ready for a DP skip the HP number and look at the torque.

And one more adder;

A friend of mine does the Northern NY to Florida run every winter with his toyhauler. A few years back his DuraMax needed more work than could be done before they were scheduled to make the trip, so he traded it in on a 6.0 gasser. The gasser made exactly one trip to Florida and back and was traded back in on another DuraMax. And not to turn this into a Ford/Chevy debate, that DuraMax was traded on a new Dodge Cummins 2 years ago, he is now shopping for a Super Duty. I will admit I am a Ford guy, but there is a reason you see so many Super Dutys pulling fivers. I'll also say none of them are bad by any stretch. If you choose to keep your fiver any new diesel truck would be sure to put a huge smile on your face.

[Effy]

I would think there are many, many factors to consider. Weight of the DP, engine, power to weight, torque, how it's loaded etc etc. One 40' DP might make it up 40 mph, another 40'er 60mph. Too many variables. Narrow to a specific coach(es).

[Leeblev]

I have a 36' DP Cummins 275 with an Allyson 5 speed tranny.
My experience going over the grapevine is 45-50 mph. The only problem with that is it is too fast for the trucks and too slow for lighter RVs. I do weigh in at 25,600 with my '11 Ford Ranger in tow. I get 11 MPG
I previously had an International 4dr 4700 with the 250 engine and an Allyson 6 speed tranny pulling a 30' 5er. My total CGVWR on that was 21500 lbs. I drove the Grapevine at 40-45 mph and got 9.8 MPG
I also drive the Siskyous (I feel steeper) and do pretty much the same thing, with both rigs.
I am happy when someone passes me 55-60 mph, because I usually pass them stopped for fuel somewhere down the line.


















Now, I am not unhappy going up/down both of the grades I mentioned at 40-50 mph. I really wouldn't want to go faster. Don't forget the 25,000 lb. weight and stopping.

[TucsonJim]

Not a Class A Response, but here is my before and after:

Before

2004 Chevrolet 2500HD extended cab 4x4 6.0L Gas
2007 Keystone Cougar FW (Approx 9800#)
Speed on 6% grade - 35-40mph.

After

2013 Ford F350 Crew Cab, 4x4 6.7L Diesel
2014 Grand Design Reflection (Approx 12,900#)
Speed on 6% grade - 60-65mph with more pedal if I needed it!

Granted, the Chevy was 10 years older, and only had the 4 speed transmission. You can stay with a fifth wheel if desired and have all the power you need. But I'm guessing that if you want a MH, you'll see similar results in the power plants.