Cummins Diesel Upgrade to Classic MH

[guy99]

I've been thinking about a diesel re-power for a while. I have, however, read a little about the truly serious health effects of dirty diesels so if I do it I would want a 'clean' implmentation. It would be a different matter if biodiesel was a viable option for someone who drives a lot (44,000 miles in 29 months). But the availability is not great enough.

So I remain on the fence, looking for a way to convert to a clean diesel solution.

[GlenCoombe]

Guy, if you can manage the engine swap bio-diesel is easy. Why not brew your own?

[swebster]

guy, it interests me as well. I like the idea of an SVO conversion since my usage patterns are typically a number of close to home trips througout the year with one or two big trips. I like the idea of SVO for summer local camping but with the convienance of deisel for cross country excursions.

Mostly I like the idea of having choices in fuels.

But, this is not the primary motivation for a conversion in my book. One of the topics we all discussed was the longevity of the coack itself and how long an owner can get out of a Classic Motorhome with the right powerplant.

I do know the newer engines burn much cleaner and so they might be a better option for you.

[Wayne Olson]

I think it is important to be sure the entire power train is planned out BEFORE YOU START A CONVERSION. The engine, transmission and rearend all have to be geared correctly to work together for best mileage and operating speeds. A good target would be 2000 RPM equal to 65 MPH.

Our 345 conversion was done starting with a new Cummins Diesel 6BTA5.9 crate engine and a new Allison AT542 4-speed Transmission. This has been a very reliable setup and has a very long expected service life (well over 250,000 miles). It is not fully electronic so it may have slightly lower MPG but it also is very easy to work on and any diesel shop can work on it. Much of the work could even be done in the driveway such as injection pumps, injectors, fuel pumps, etc. with no special tools, computers or electronic equipment needed. It would be much more difficult to convert to a fully electronic installation, especially when it comes to the transmission and cruise control setup. I also have a 2004 Ford F350 PS Turbo Diesel. It is fully electronic and it needs to be serviced by FORD since it is so complex and needs specific computer and diagnostic equipment.

On a sad note, as I explained to the guys on Sunday, we are going to sell our loved 345. It is a fact of life that the phases of our lives never last forever. My lovely wife of 30 years and I have purchased a property near Tucson AZ and plan on grounding ourselves more than we have in the past. We have loved all the 345's we have owned and restored. Robfike is now driving one of our prior 345's to pull his race car. However, this 345 has always been special to us. It needs to be loved and driven, not just sitting in our barn waiting for us to come home.

Wayne

[outofcontrol]

Those are spot on points Wayne.

I found some stuff from my last research effort:
http://www.autoworldmt.com/Page_9.html
You can buy the motor mounts pre-fabbed and all sorts of other stuff.

I emailed this shop about doing the re-power in June: here's they're reply:

our basic labor price is $6000.00. - there really is no "basics" and "extras" everything has to be done @ the same time to make it drive away.
what people don't realize is that its not just the motor - there is a miriad of electronics, wiring etc for the 04.5 and above motor to run before that they had a throttle position sensor but you still have to deal with wiring harnesses, computers, oem wiring for the vehicle and it takes a ton of parts esp with going from gas to diesel....but it is still a worthwhile thing with the mileage and the price of the new motorhomes/trucks.
what is your thinking as far as tranmission goes????(whats in there now?)
i can put togeather a quote all inclusive, once i know those details!
dawna
p.s. we usually need the vehicle for 5-6 weeks, so if you want it for summer traveling, best to wait til after - right now we are booked into the 1st wk of august (confirmed with deposits and have one job booked to be done in october)

-Kevin

[Taxman]

Glenn, let me encourage you in the storngest possible terms to spring for the Gear Vendors Overdrive.

I have only driven my 1990 33'LY a few miles since the GV was installed (See my thread "In praise of p30 chassis/drivetrain mods"), but I am here to tell you that it is worth every penny you'll pay to get it installed!

RPM @ 60 MPH went FRom 3000 to 2500. Water Temp down FRom 200 to 190 (it'll go lower when I put the 180 degree thermostat in!). And, the coach is much quieter, as you would expect.

All in all, a most worthwhile expenditure. And since you use your coach for business purposes, the entire expense is tax FRee!

GOPHERIT! You will not regret it.

Taxman
1990 33' LY
Banks, Gear Vendors, Safe Steer, Bilsteins, Roadmaster Anti-sway bar, Super Steer Bell Cranks.
WBCCI 6416

[GlenCoombe]

Taxman, I find it interesting that you get only 500 rpm of relief on your GV. I was thinking in the range of 700-750 rpm reduction. That's what has me hesitating. I run 3000 at 65 mph so the original drop would have me close to a lugging rpm IMO. Is your rig a 3spd or 4spd tranny?
I agree with the whole principal of lower rpms for piece of mind through reduced engine noise, lower temps...etc.
As to being tax free it still has to be earned before it can be spent! But it's a new year and a new budget too.

[str8strm]

Glen our rpm drop is right at 600 and it does make a big difference!!..Last trip somehow a bad connection in our headlight dimmer switch took the unit temporarily out of service and we really noticed the rpm difference. It felt like we were over revving the motor. It is a very nice unit to have ... although it makes it too easy to go fast cos you don't even notice it. Debbie

[cooperhawk]

Okay, maybe I'm all wet here but when I worked with my father in his trucking company we adjusted the ring and pinion ratios to adjust rpm's to speed. Since the 345 is on a Chevy bus frame there should be plenty of ring gears available to change the ratio. Why isn't that an alternative?

I have been thinking of doing just that. A good friend has a shop just up the road where he does this kind of work. I know enough about it to be aware of how critical the shimming is.

[Taxman]

Glenn,

As I understand it, the GV is supposed to be a 22% reduction in RPM for a given speed. Accordingly, I should see roughly 2500 RPM (3000/1.22) with the overdrive engaged at 3000 RPM.

I may have been driving 65, BTW. I didn't write any of the data down, and was experimenting with 60 and 65 MPH cruise. The coach seemed equally at ease at 65 as 60.

It is possible, mind you, that in my excitement as to how nice my "new" ride was, what with the chassis and engine mods, I misread my instruments on the way back FRom St. Augustine.

I'm taking a 250 mile trip this coming weekend, and I'll pay a lot more attention to it this time. Heck, I may even write some of this stuff down on paper so I won't have to rely on my old age and decrepitude impaired memory!

Check out the FairTax website at Americans For Fair Taxation - FairTax.org. Lotta good information there about the National Retail Sales Tax.

[Taxman]

Glen,

Follow up: I don't think youi'd be in any danger of "lugging" your big block @ 2500 RPM. I had a Banks Power Pack kit installed, which is supposed to improve low end torque and HP -- and my seat of the pants impression is that it does, significantly!

HST, I recall reading your posts about the mods you made to your coach, and I do recall that you made a cold air box and installed a good set of dual exhausts. IOW, you also improved the low RPM torqe/HP characteristics of your big block Chevvy -- maybe not as much as the Banks, but certainly enough to handle 2500 RPM cruise. I think you will be OK with the GV.

BTW, I have a 6 speed transmission now: 1st, 1st over, 2nd, 2nd over, 3rd and 3rd over. LOL! It started life as a three speed Turbo 400 (475?). Then it went through a GV transplant.

I am a huge fan of the GV, even though I have only driven it a few miles since the installation. Worth every penny!

[GlenCoombe]

Taxman, my concern is that at 70 MPH I'm turning 3100 rpm. If I drop it down by 22% then I'm at 2400+/- and that's what has me concerned. If I then have to back down to 65 or less I'm getting into lug / shift range. How is the GV unit as far as sensing downshift needs?
I kind of feel like my rpm range has me at a disadvantage as I'm already lower than most.
The lack of folks changing rearend ratios is likely a result of the specialized tools needed to do the job right. It's not as simple as a swap of parts. The shimming of the gears is crucial to a long lasting and non-howling rearend.
It's almost like I need to do both a rearend swap and a GV to get to where I need or want to be.....
All I want is to get home so I can get back to work on it before I leave for Florida the end of Jan. I've got to get my new generator in next week for certain.

BTW... live from NE of Toronto today....brrrrrrrrr

[cooperhawk]

Originally Posted by GlenCoombe

The lack of folks changing rearend ratios is likely a result of the specialized tools needed to do the job right. It's not as simple as a swap of parts. The shimming of the gears is crucial to a long lasting and non-howling rearend.
It's almost like I need to do both a rearend swap and a GV to get to where I need or want to be.....
BTW... live from NE of Toronto today....brrrrrrrrr

The farm guy up the road from me works on trucks in his shop. I'm going to see what he estimates as to cost to change the rear end ratio. I'm sure he has all the equipment. I'm not worried about lugging the diesel very much. At 65 mph I am turning 30000 rpms as well. 2200 would be okay. I still have plenty of power, but the power curve is right around 2400rpm's.

[Taxman]

Glen,

When you drive down to Floriduh, please leave the cold weather up there!

When I do the math on your RPM reduction with a GV, I get 2541 RPM (3100/1.22). With your engine mods, that should be right in the "Sweet Spot."

BTW, if I recall correctly, you installed a MSD 6 ignition. Is that correct? You need to keep your RPM below 3000 to get mutiple spark discharges. Above 3000 RPM, the MSD fires each plug once.

I'd not give much thought to a new ring and pinion unless you need to have your RE rebuilt. My guess is that the GV is cheaper and far more useful.

And, BTW, you do not need, nor do you want, both a GV and a different gear ratio. Your engine will pull 2500 all day long, and love it!

I just had a wild thought: convert your engine to a Throttle Body Fuel Injection setup. If you are interested, email me at fdavis@salestax.org and I'll send you the info I have about the TBI upgrade. My 1990 LY has TBI (as does my 1991 Cadillac Fleetwood Brougham), and I love the TBI setup. It is simple, it works, and it is maintenance FRee!

[Taxman]

[quote=As to being tax free it still has to be earned before it can be spent! But it's a new year and a new budget too.[/quote]

Roger that!

BTW, how do you make money selling golf stuff in the wintertime up there in Canada? Kinda hard to demo a new club head or shaft in the snow and cold, isn't it?

[str8strm]

When we bought our 345 last year, the GV was already in it. I didn't know what it was (and it wasn't working) so I didn't miss it. Once we got more info, we got it repaired and my RPM dropped from 2800 at about 60-65 mph to 2200. The 454 runs quieter, cooler, and still pulls great when I need it. I am definitly a fan. Unfortunately, I can't tell you what my rear end ratio is. Ron

[Taxman]

Ron,

I had decided before I bought my LY that I wanted a GV and the Banks Power Pack. We drove the MH FRom Grand Rapids, MI to Jacksonville, FL and I made arrangements as soon as I could to get the GV and Banks installed, along with some other chassis work I wanted done.

We are delighted! I don't get the RPM drop you get, but I'll take 2500 vs 3000 RPM any day! Hopefully, we'll get better gas mileage, also, but even if we don't, the GV was worth every penny we paid to have it installed.

There is a way to determine your gear ratio -- the next time you have the coah up on jack stands, mark the driveshaft with a piece of chalk and turn one of the wheels one complete revolution. Number of revolutions on the driveshaft (i.e. 4.5) for one revolution of the tire is your final drive ratio.

Now, I realize that it is not too often that our coaches get up in the air like that, but should you ever have it off the ground and are still curious about your final drive ratio, that is one way to find out.

FRank

[outofcontrol]

I know this is an old thread, but every time I drive my MoHo I think about how nice a 5.9 cummins would be on power and efficiency. It will be another 3-5 years before I do this conversion, but I'm always on the prowl for advice, and a source for a donor vehicle. I was surprised to find out that a lot of early 90's school busses have this combo, and you can buy the whole bus for pretty cheap; 2500-4000. I found plenty of them on craigslist, but here's another source: Welcome to First Student there's about 21 of them in Oregon right now, and most are 5.9 cummins/4sp Allison.

cheers!
-Kevin

[swebster]

Kevin,
I think about it a lot but lately when I'm filling up the 345 I really think about it.

What do you think about the Isuzu four bangers? Here is a post I put on ThisOldRV.com about a recent opportunity to buy this motor cheap:

OK, so I'm just spitballing here but I recently was presented with an opportunity to purchase an Isusu Box truck for not a lot of money which uses the Isuzu 4HE1TC turbocharged engine. The truck is a refer 16' at 14,500 GVW. A check on the Isusu commercial site shows this engine in their N series trucks up to 17,500 GVW.

Specs on the engine at 175 hp @ 2,700 rpm and 358 ft-lbs @ 2,000 rpm.

Maybe I'm crazy but since the 454 is a 240 horse / 355 torque motor....is it feasable to consider a 4 cyl engine as a replacement in my 16,500 lb Airstream? Seems like the torque is there but will the HP be an issue?

This is a complete truck along with the tranny (4 speeds with ODrive) and all of the bits and pieces.

[87MH]

I've bit my tongue on posting to this thread before, but if you are seriously thinking of a swap by all means check how much weight allowable you have left on the front axle. 4 cylinder swaps excepted.

I am almost over the allowed with just the changes in the interior.

Remember, the P-3X is basicaly a one-ton chassis, and most of these 345's have been sitting with a full 4 tons on them for 25 or 30 years.

I would have to think long and hard about what sort of a benefit - and how long it would take to pay out - before I dropped a Diesel into a 345 P Chassis.

Of course, with a 4 cylinder Isuzu under the dog house (pun intended) I would have PLENTY of time to think about all sorts of things while I accelerated (or tried to) into merging Interstate traffic.