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I own a Winnebago Trend 24ft RV based on the Promaster 3500 Cutaway chassis. The V6 engine seems to do ok (not exceptional) for for for such a small engine in a small full featured RV chassis. I was really looking for the diesel version of the Promaser, but who knows if that will ever happen. It only has 3K miles on it and MPG is about 13MPG with mostly back roads driving.

My question is with such a heavy load on the 3500 Promaser with the RV chassis (7000 lbs estimate not got to have it on the scales yet) is it best to operate the Promaster in the "Tow/Haul mode" the manual states it should be used for heavy loads and towing and it adjusts the transmission shift points, to reduce up and down shifts, and assist in braking / down shifts. I would assume less MPG in this mode but would think with such a heavy load on the Promaster RV all the time it would be best for the Engine / Transmission operation and reliabliity.

Any other Promaser RV or heavy duty users or expert views on this ?

Thanks
John
 

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Although I don't know the answer, I can via experience with my trucks over the years, tell you what happens to a transmission when you don't use tow mode, when you should have.

The transmission runs too hot. The first telltale sign of a hot transmission is slippage. You'll notice when pulling away from a red light, the RPMs run higher than normal for each gear. You'll hear it. No tach watching required.
 

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I wouldnt expect too much from the diesel engine. You would be giving up
approximately 100hp and gaining 30lbs ft of torque. The vehicle would accelerate considerably slower, since hp provides the acceleration to merge into traffic. Torque will allow you to maintain the desired speed easier once the cruising speed is reached. The gas engine does provide 90% of the 260lbs ft of torque from 1900rom on up. And I know the feeling of wanting a little more when I tow my trailer. But I dont think the diesel will be much better. Also given identical driving conditions and driving habits my guess would be that one will see about 5mpg increase with the diesel option when it becomes available. Current gasoline prices at $310 per gallon compared to $365 per diesel gallon and Urea, the fuel amount savings will not be great!
 

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High horsepower low torque engines (Ferrari for example) accelerate very fast .
Tractor Semis have 1400lbs ft of torque and about 400hp. Torque will get you going of the line and HP takes over to accelerate you to speed. Up a mountain high torque engines have a better ability to maintain the speed before speed starts dropping. But accelerating up a mountain to gain MPH that would be HP that does the job.
 

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I own a Winnebago Trend 24ft RV based on the Promaster 3500 Cutaway chassis. The V6 engine seems to do ok (not exceptional) for for for such a small engine in a small full featured RV chassis. I was really looking for the diesel version of the Promaser, but who knows if that will ever happen. It only has 3K miles on it and MPG is about 13MPG with mostly back roads driving.

My question is with such a heavy load on the 3500 Promaser with the RV chassis (7000 lbs estimate not got to have it on the scales yet) is it best to operate the Promaster in the "Tow/Haul mode" the manual states it should be used for heavy loads and towing and it adjusts the transmission shift points, to reduce up and down shifts, and assist in braking / down shifts. I would assume less MPG in this mode but would think with such a heavy load on the Promaster RV all the time it would be best for the Engine / Transmission operation and reliabliity.

Any other Promaser RV or heavy duty users or expert views on this ?

Thanks
John
You might post your question on the Trend / Viva yahoo group...there are owners there who have driven their Trends in the mountains and may have a suggestion.

https://groups.yahoo.com/neo/groups/Viva-Trend/info
 

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I've been playing with the Tow/Haul button a bit in mountains and with or without heavy loads. All it does really is increase the shift points and hold them longer, but it does have a quite an effect on hill descent. The transmission will basically try to engine brake for you, somewhat predictively. In other words, if you were just coasting down a hill picking up speed in regular mode, in tow/haul the trans would downshift as you started picking up speed.

In truth, you can do the same thing by shifting manually (the PM has a manual gate on the shifter).

I can tell you that my 3500 extended weighs 5240 empty, and is rated to carry 4200, so at 7000 you're not really all that heavy. With 3000 in the back of mine, you barely notice a difference in handling or accel.

Lastly, torque is a measure of force, and horsepower is a measure of power which means work through time. So hp is a measure of how fast you can apply a given torque. It's not accurate, but as used by gear heads torque generally refers to low rpm power, and hp to high rpm power.
 

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12.5 mpg Dynamax REV

I own a Winnebago Trend 24ft RV based on the Promaster 3500 Cutaway chassis. The V6 engine seems to do ok (not exceptional) for for for such a small engine in a small full featured RV chassis. I was really looking for the diesel version of the Promaser, but who knows if that will ever happen. It only has 3K miles on it and MPG is about 13MPG with mostly back roads driving.

My question is with such a heavy load on the 3500 Promaser with the RV chassis (7000 lbs estimate not got to have it on the scales yet) is it best to operate the Promaster in the "Tow/Haul mode" the manual states it should be used for heavy loads and towing and it adjusts the transmission shift points, to reduce up and down shifts, and assist in braking / down shifts. I would assume less MPG in this mode but would think with such a heavy load on the Promaster RV all the time it would be best for the Engine / Transmission operation and reliabliity.

Any other Promaser RV or heavy duty users or expert views on this ?

Thanks
John
On level Interstate 70 mph cruise my Promaster 3500 based Dynamax REV (same as Trend) with 2000 mi averages 12.5 mpg. Instant gauge says 14 mpg in 6th, 12 mpg in 5th, 10 mpg in 4th with cruise set to 70 mph. In D it continually downshifts to 5th so averages close to the 5th gear 12 mpg.

Dynamax weighs every RV at shipping. Dry weight was 8024 lb and right rear wheel was only 90 lb less than GAWR/2. The dealer filled gas, propane and water and after I bought it the DOT scale said rear axle was only 60 lb less than GAWR. When I step in the back door the right rear wheel is 200 lb over safe load rating as defined by Ram with no passengers or cargo.
 

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Winnebago Trend Exceeds Rear GAWR??

I own a Winnebago Trend 24ft RV based on the Promaster 3500 Cutaway chassis. The V6 engine seems to do ok (not exceptional) for for for such a small engine in a small full featured RV chassis. I was really looking for the diesel version of the Promaser, but who knows if that will ever happen. It only has 3K miles on it and MPG is about 13MPG with mostly back roads driving.

My question is with such a heavy load on the 3500 Promaser with the RV chassis (7000 lbs estimate not got to have it on the scales yet) is it best to operate the Promaster in the "Tow/Haul mode" the manual states it should be used for heavy loads and towing and it adjusts the transmission shift points, to reduce up and down shifts, and assist in braking / down shifts. I would assume less MPG in this mode but would think with such a heavy load on the Promaster RV all the time it would be best for the Engine / Transmission operation and reliabliity.

Any other Promaser RV or heavy duty users or expert views on this ?

Thanks
John
When I found out the Dynamax REV is engineered to have an overweight unsafe rear axle weight during normal use I called Winnebago tech support since the Trend 23RB is basically same as Dynamax REV 24RB. He said Trend is 200 lb less dry weight but refused to tell me the dry weight of individual wheels or axles. I'm convinced it is an industry wide problem to overload rear axles. I also think the industry lobbied NHTSA to NOT include front and rear axle dry weights or cargo capacities on the Cargo Capacity tag legislation. The manufacturer and dealer are not responsible for exceeding GAWR since it was within GAWR rating when it left factory dry. It is the owners fault if he wants to fill the water tank or carry a passenger or two. The owner can always balance the load and stay within load ratings if he drains the gas tank and propane before adding water.
 

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The weight ratings of the pm (and every vehicle ever made) are not set in stone kind of numbers. You could take your pm, put 20 thousand pounds on it, and it's not like the axles would snap or the tires would pop.

The tires would get hot, and wear out sooner than the tire warrany specifies. Fca builds the transmission such that you can load it to spec, floor it up pikes peak in the summer, and it will last to 50,000 miles. Overload it and it might last only 40,000.

Brakes will stop a fully loaded pm in whatever distance its rated at by nhtsa. Overload it and stopping distance will increase, and brake life will shorten. Nothing more.

The pm is rated to pull 5000lbs, and when doing so its braking and steering meets code. It WILL pull 30,000 lbs no problem. But it wont stop or steer or accelerate like it will at 5,000.

My point? The specs are based almost entirely on safety and durability, and because of litigation thry are super conservative. Relax.
 
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