Considering Diesel A - 275 hp Cummins questions?

[AstroRig57]

After selling our 32' Class-C gasser, and considering whether to go with a TT or Class-A motor home, we've decided on a Class-A and are now working on our "short list"

I thought I wanted another gas rig but, to my surprise, we've found a diesel pusher rig with which we are pretty well enamored. I know, you've probably answered these ad-nauseum, but here's a few questions I have.

The rig were looking at right now is a fairly late model, used, 36' Winnebago on a Freightliner chassis, 26,350 lb GVW. It has a 275hp Cummins Turbo Diesel and Allison transmission. My question is, is that engine powerful enough so a rig that size can even get out of it's own way? I know diesels have different torque characteristics than gas engines but have no idea if the 275hp Cummins would be considered a bit anemic for this rig or not? On steep grades, will we be the slowest thing on the road?

Also, in regard to the cost of fuel, the days of diesel being cheaper than gas are long since past especially in CA with the low sulfer diesel requirements. How does fuel mileage on a diesel pusher compare with that of a comparably sized gasser? Does better mileage offset the higher price of diesel or not?

I won't ask the questions re maintenance costs etc., as I've seen those pretty well covered. Also, this rig will be out at least 2-3 weekends a month so the "can I let it sit" question is a moot point as well.

Thanks

[Greyghost]

Since you're near Tehachapi, see if you can test drive it up the Grapevine. That should tell you want you want to know about the capabilities of the coach. Or, drive it up and down 58 for a test.

[mtrumpet]

AstroRig57 wrote:
After selling our 32' Class-C gasser, and considering whether to go with a TT or Class-A motor home, we've decided on a Class-A and are now working on our "short list"

I thought I wanted another gas rig but, to my surprise, we've found a diesel pusher rig with which we are pretty well enamored. I know, you've probably answered these ad-nauseum, but here's a few questions I have.

The rig were looking at right now is a fairly late model, used, 36' Winnebago on a Freightliner chassis, 26,350 lb GVW. It has a 275hp Cummins Turbo Diesel and Allison transmission. My question is, is that engine powerful enough so a rig that size can even get out of it's own way? I know diesels have different torque characteristics than gas engines but have no idea if the 275hp Cummins would be considered a bit anemic for this rig or not? On steep grades, will we be the slowest thing on the road?

Also, in regard to the cost of fuel, the days of diesel being cheaper than gas are long since past especially in CA with the low sulfer diesel requirements. How does fuel mileage on a diesel pusher compare with that of a comparably sized gasser? Does better mileage offset the higher price of diesel or not?

I won't ask the questions re maintenance costs etc., as I've seen those pretty well covered. Also, this rig will be out at least 2-3 weekends a month so the "can I let it sit" question is a moot point as well.

Thanks

Although you won't win any races, that Cummins 275hp engine will be fine for that size of rig.

Unless I missed it, I do not see anywhere where the OP mentioned the model year of the unit in question, although, being a 275hp Cummins, I guess we have to assume late 90's/early 2000's. Having said that, does it come with air suspension? (Some older models did not.)

[glamisorbust]

My coach is a 1999 holiday rambler endeavor on a freightliner chassis. I've owned multiple gas coaches in the past. This is a major improvement over any of the gas rigs i've owned.

The 275 HP cummins is plenty adequate for the task. On mountain grades in between phoenix and flagstaff, AZ(large, long grades), even pulling a honda CRV, I never drop below 45 MPH.

Mine does have the "53 block" which was manufactured in brazil for a short period and they are known for cracking. However, if they are warmed up and cooled down properly this probably won't happen. Drive it like you want it to run tomorrow and you're good to go.

I average 10.5 MPG with just the RV cruising about 65 MPH. I towed my large flatbed the other day to the dunes and back, mostly flat and about 60 MPH. I got about 9.5 while towing. The transmission will downshift to 5th even on small freeway overpass hills, and if it needs to, it will shift to 4th. No need to be alarmed, these engines can handle RPM's with ease.

The other major problem on these generation cummins is the VP44 injection pump. The stock lift pump(fuel pump) is mounted on the engine and gets a lot of vibration. When it starts to fail, the injection pump will start sucking fuel instead of being supplied fuel from the pump. The outcome is never good and ends up destroying the injection pump. There are two things you can do: If you do buy this coach or one like it, put in a fuel pressure gauge you can watch while you drive. If it drops below 5 PSI your pump is probably weak.

Also, you'll want to run a fuel additive like power service to replace the sulfer they started taking out of the diesel fuel. I have had my coach for a year and half and I absolutely am in love with it. Feel free to PM me if you have any more specific questions.

[LongWeekends]

RayChez wrote:


Lots of RVers like Cummins, but they do not compare with Caterpillar engines. They last for ever.

Painting with a broad brush there. I had my coach in Freightliner for service and they said the opposite, they prefer the Cummins over Cat all day. The Cat repairs are much more costly and frequent according to them and they work on all makes every day. FWIW...

[Kayteg1]

I don't think even 1000 hp in 3x' long coach will be adequate as my 7000lb pickup has 350 hp. 😉
But you don't expect to race BMW with your motorhome like I do with my pickup.
Anyway, I drove diesels exclusively for last 15 years and lately, since diesel wagons are not available in US, I had to buy gasoline wagon.
So last car was the same model of MB Eclass with 174HP diesel. Then newer one has 230HP gasoline engine.
In normal driving gasoline engine feels weaker due to low torque at cruising speed. Where lower HP diesel would make to top of the grade without downshifting, the 30% more powerful gas engine has to downshift.
It comes more clear why if you can compare HP diagrams at cruising speeds, but that is how it works in real life.

[RayChez]

tinkerer wrote:
I don't know what year it is but be careful of one manufactured from 1998 to 2002 as some of them had bad block that crack. Have a Cummins expert take a look at it and if it has a block identified as a #53 block run away from it.;)

I completely agree with this post. I blew a couple of these engines that were manufactured south of the border. They will blow up and it was not pulling that much weight.

Lots of RVers like Cummins, but they do not compare with Caterpillar engines. They last for ever.

[wolfe10]

More info on #53 Block issues: http://www.cumminsdieselspecs.com/cummins-53-block.html

[tinkerer]

I don't know what year it is but be careful of one manufactured from 1998 to 2002 as some of them had bad block that crack. Have a Cummins expert take a look at it and if it has a block identified as a #53 block run away from it.;)

[Kiethco]

I agree with Hershey. I have a 34' Holiday Rambler with the 275 ISB and Allison. I heard the same thing about being a dog on long hills. I can pull any hill at 35-40 the Conejo grade, the 40 coming out of Needles and the Cajon pass heading up the 15. I'm on those hills for 10 minutes or so. I don't mind chugging up at those speeds, I'm still flying past semi's!
The sweet spot is 62 mph as stated, about 1700 rpm. I get a solid 10 mpg. I'd stay away from the chips, and mods. I had a friend with Banks, they're great products but once you start..............

[John_Wayne]

Not sure but I think you can chip up the horse power IF you have the 6 spd trans and not the 5spd trans. The smaller 5 speed trans. can't handle the extra torque.

[Mote]

tinkerer wrote:
I originally had a 275 hp 5.9 Cummins and it did ok, but it was gasping for breath a quite a bit,and be careful of those 275 hp 5,9's as the blocks like to crack on them causing a $19,000 bill for a replacement engine. I know because it happened to me. I have a CAT now and would never buy a coach with a small block Cummins again.;)

There were some 5.9l blocks in the 1999-2000 time frame that had a thin wall area. They would have the number "53" cast in the block near the oil pan.
If the engine does not have the 53 block then you will not have issues with a cracked block.

[P_Kennedy]

Their are thousands of these little engines out there in multiple applications doing a great job without issues everyday some with mega miles on them. The cracking blocks were the infamous #53 casting in which there was some failures but it was not every block and there was some warranty offered. The biggest question here seems to be whether or not you can live with a reduced speed going up and down grades with a vehicle bigger than a Honda Civic. Read through some of the posts with the HP vs Weight discussions and you will quickly realize 2000 hp in a 40,000 lb motorhome is way under powered because BillyBob could not pass a Maserati on I70 going up the grade to the tunnel. Tinkerer sorry you had one of the bad ones but $19k is not going to cover the bill if your kitty has a hemorrhage, they have had issues too! If a man made it, it will break.

[tinkerer]

I originally had a 275 hp 5.9 Cummins and it did ok, but it was gasping for breath a quite a bit,and be careful of those 275 hp 5,9's as the blocks like to crack on them causing a $19,000 bill for a replacement engine. I know because it happened to me. I have a CAT now and would never buy a coach with a small block Cummins again.;)

[Kiethco]

I have a 1998 HR Endeavor 34' with the ISB 275 hp and Allison. I just got back from Quartzite, a 500 mile roundtrip. I had an easy drive at 62 mph with cruise control on most of the way. On any grade between LA and AZ up to about 5%, the trans would shift down to 4th but held at 60 mph. I got real close to 10 mpg over the trip.
When I take the hwy 101 over the Conejo grade going up the CA coast, which I think is about 7%, I do drop to 45 mph and hold that speed.
For me, this little package is the engine that could and does.