Hi Everyone,

I'm looking for some guidance before I purchase an RV. One is a class 'C' and comes with a Duramax engine on a Chevy 5500 chasis (Jayco Seneca). It has an Allison 1000 transsmission in it.

The other is a Fleetwood product that has a CAT engine in it.

I've heard rumors that the Duramax is a 'glorified gas engine'. I've heard others say that it's the best there is.

I'm looking for some guidance as to the engine itself as as to which is better based on reliability / power / performance / maintenance?

Thank you!!

Chris

The Duramax is a great engine. That said, when I went for a class 5 truck, I decided on something a little out of the ordinary when specing the powertrain.

I went with the low HP engine.
Taller rear gears.
6 speed Allison.

MBE 270hp/890tq 5.22 rear gears, Allison HS3500/V transmission.

Basically, the Allison has the double OD keeping the motor in it's happy place (near peak torque) better even with 5.22 gears.

Remember HP= fuel economy. Higher 'natural' torque more than absolute HP pays dividends in keeping the load moving in the worst of hills, with far less strain than working the higher HP motor. In practice, the motor in the freightliner gives us 15 mpg unloaded, and at max insured weight, we see 10 mpg.

The best thing is that 5th gear is overdrive #1. In mountain passes, 5th or even 4th becomes the norm, while on the flats, 6th gear provides for fuel economy.

When specing out the next truck (whenever we wear this one out) I will make the same choice. High torque low HP of the same basic engine. The engine choices were 350/330/270hp. TQ was 920/900/890. Of 3 identical trucks in our area, we are getting the best overall economy. In fact, the Allison has proven to be 1 mpg better than the Roadranger 9 speeds.

Personally, I would look at the powertrain options, then take one of each out for a drive. AND find a hill to drive up to see the difference.

That's some good info right there.

What is the displacement of the MBE?

Caterpillar. If the price was similar, I think you've just got a stronger motor there. Good luck to you.

What is the weight on the rv?????? Where are you planning on camping, in the mountains, flat ground???? How many miles are you putting on in a year????? If yoru gonna live in it, be in it all day, you may want more power. In the 5500 imo, is pushing it for the duramax. If your puulling a toy hauler, or boat w/the camper you amy look to the cat. The nice thing about aht, most truck dealers are cat certified (know waht they are doing, and can warrenty), and are open 24x7. Cat medium duty motors arent anything to brag about imo, they ahd their share of problems. Maybe step up to a 6500 cahsis and get the d max 7.8 is that possible.

that's some good info right there. What is the displacement of the mbe? 6.4l

Here is the info on the Duramax:

Duramax 6600 V8 Turbo. The GVW is: 22,000 pounds

It's going to be for weekend use and perhaps a couple weeks of travel out of the year. I would likely be towing a boat on occasion. I have a family of 6, and two inlaws that like to come along. It's in a super "C" motorhome (Jayco Seneca) that I have heard mixed reviews on.

When I started hearing about the engine, some rave about it, some say it's not so great. I'm trying to decide between this motorhome and the larger one with the CAT engine.

This one is cheaper, but I'm trying to steer clear of problems down the road.

Thanks for the info!! Considering the above, would the Duramax be up for the load?

THanks!
Chris

i think you may need to look for an rv forum and ask the people that actually own one. that way you can get a few different opinions. I have driven 1 medium duty with a duramax. That thing ran great. I have also driven a few different medium duties with cats and those feel slow but you can tell they will pull just about anything. Thats all the info i have... i recommend finding an rv forum though. Post up what you find / what decision you make and why.

great post Juice :cool:

ben

For what you say youll be doing I would say that either would be fine, I would look at price and gas mileage especially if your going to be taking long trips.

Good Luck!

Id say the cat at that point or jump up to a larger motor home and get a 7.8 liter d max or a 8.3 cummins, esp if the boat is a decent sized one

check this forum out it is all about rvs and they can help you out. www.escapees.com I have a c4500 kodiak and have towed a couple of larger boats with it and had no troubles granted our only "mountain" is the Arbuckles. Didnt need to get in the slow lane with it. For upgrades the Cat cost a lot more to get. U You can get the ambulance pkg hp ratings but only like 30 hp more the same as a duramax. The duramax you can power up to almost what you want.

Id say the cat at that point or jump up to a larger motor home and get a 7.8 liter d max or a 8.3 cummins, esp if the boat is a decent sized one


One thing I have learned (if there is anything to be taken away from my posting) is that overall gearing, and gradeability with the transmission and rear end ratios are as impotrant as engine output.

With enough gears 'low' HP/hi TQ motors will outperform/outpull/get better mileage than an engine with more HP, and less gear split/5.88's or better in the rear.

When purchasing the FL, the hardest choices I made were on the transmission, and the rearend ratio.

I had a choice of the HS3500/6 W 5.88's 6th@65mph=2250 at gov 2750
or I the choice that i made HS3500/6 W 5.22's 6th@65mph=1900 at gov 2750

with the 5.88's you are running over the top of peak TQ, whereas the 5.22's are 250 rpms into the meat of the TQ curve.

Translation: better fuel mileage as the engine is not working or revving unduly high to maintain speed. Of course, on a grade, you might have to downshift to 5th gear, and with 5.22's maintaining 65 mph is done at 2250 rpms.

Gearing on a heavy vehicle with large frontal area is more important than the raw HP numbers. I know Cummins has a place on their site where you can spec the vehicle, the cummins engine, then do a gradeability of transmission and gearing choices.

Good Luck!

More great info. For what it's worth, my 3500 Duramax weighs in at 10,400, and you are getting MUCH better MPG than me.

Best advice is keep it in the torque curve.

If it is the CAT "C7" or 3126 engine, stay away from it!

I owned a 330Hp RV model and it was a real POS.
The valvetrain kept dropping valved and toasting the motor. I wasn't real impressed with the performance of the motor either..

Go for the Duramax, it's a more reliable choice!


--Chuck

I have a c5500 04' with the alison duramax combination with a 19500 GVW and tow 18000 all day long and it pulls like a bear. mpg is about 12 as a matter in fact we also have a top kick 7500 with a 300hp cat and the Duramax will out pull it hands down!

My father is a truck driver, and has been for the past 25 years. If you mention CAT in front of him, he will go on a yelling spree. He said I coudnt pay him to drive one of their POS motors. Apperantly he had a couple real bad experiences

For what the Seneca's have climbed to price wise I would look more at the "entry level" class a diesel pushers. I have a friend that races and he has tried more trucks and rv's and is now running a diesel pusher and is much happier than he ever was using a super c or 4500 hauler. If you shop you can get into a pusher for not much more than the Seneca.

Beware or heavy hauling/pulling with a pusher, particularly stock. the cooling system , IMHO isn't great and , combined with stock mufflers, the EGTs will eventually fry the head gasket or worse!