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FMC #1046 converted from Chrysler 440 to Duramax diesel

BigRabbitMan
Explorer
Explorer
A year or so ago I posted about my upgrade project with my FMC motor coach. FMC's were built from 1973 to 1976 with 1,050 produced so mine is the fourth from the last one built. I have owned it since late 1999 and have put a little over 50,000 miles on it. It served me well in the original configuration, but sometimes one gets an urge to do something different. A percentage of units have been converted to older mechanically injected diesel engines. Having seen that and having been around diesel equipment, I decided to convert mine to diesel as well.

After much research, I decided that the best conversion would be to a modern computer controlled engine and transmission. Of course that complicated the project, but if I was going to do it I was going to do it all the way. Considering many issues and specifications, I settled on a GM Duramax 6.6L turbo diesel with 6 speed Allison as being the ideal unit to install.

Well, the project started in early 2011 and, with interruptions such as moving from CA to OR and then buying and rebuilding a house, the project is now all but complete. Only a few wires to connect and to finish bleeding and adjusting the brakes. It is now down off of the jack stands!

For anyone who has an interest in these kinds of things, here is a link to a photo album with explanatory captions of the project. There are about 370 photos so feel free to skip over many of them!

The reason I am posting now is that some people wanted to know how the project is turning out. The good news is that we started the engine a few days ago and anticipate starting road tests tomorrow or the next day.

Here is the link to the photo album.

Here a link to my Vimeo account where the videos of the engine running are located: Start up video. Note that we incorporated the ability to start the engine from either up front or from the engine compartment.

Second longer video.

At the FMC Ownerss Club website there is also a discussion thread in the Mechanics section about the Dieselfication of 1046 where the project was discussed over time.

Enjoy,
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."
31 REPLIES 31

JetAonly
Explorer
Explorer
BigRabbitMan wrote:

Sorry for the speech, but proper, safe grade decent is a sore subject with me based on living a number years at the base of a 15 mile grade, driven light and medium trucks from time to time and having seen the results of improper decending.

Thanks for the question as you identified an important point.


No worries! What goes up must come down. Nicely done!
2000 Monaco Dynasty
ISC350

BigRabbitMan
Explorer
Explorer
JetAonly wrote:
Very interesting! The two Duramax I owned had grade braking, and later models have an exhaust brake. You don't mention what year engine/transmission your used. You might find those features useful.

My engine and transmission are from a 2006 GMC Sierra. GM insituted those features later. However, Banks has a unit called a Speedbrake that enables the variable vane turbo in my unit to be an exhaust brake. Tow/haul mode engages the torque converter clutch and changes the shift points to a higher point which is the grade brake feature. I have been able very easily control downhill speeds by simply engaging tow/haul mode and easily shifting down using the electronic shifting capability of the 6 speed Allison. In 3rd gear I desend 6% grades at 50-55 mph and 3300-3500 rpm. The engine red lines.at about 4800 rpm. First gear will bring me down very steep grades like 11-12% without using the brakes.

I had all the wheel bearings (which includes the rear wheels due to the swing axel independent suspension in the rear) packed and the brakes inspected while on this trip. The shoes still look almost new even though they were installed 15 years and 65,000 miles ago when I first bought the coach. While still a gas coach I used the engine for grade decent. I cringe when people talk about brakes heating up on grades. All coaches can and should be coming down with the engine as the brake, not the foot pedal. Brakes are for stopping, not speed control. If you need use the brakes coming down a grade, you are in too high of a gear.

Sorry for the speech, but proper, safe grade decent is a sore subject with me based on living a number years at the base of a 15 mile grade, driven light and medium trucks from time to time and having seen the results of improper decending.

Thanks for the question as you identified an important point.
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."

BigRabbitMan
Explorer
Explorer
EdNdonna wrote:
That's cool. do you still come to the tulare farm show?

I haven't yet due to having moved to Oregon and rebuilding a house and finishing the install. Plan on doing so in another year or so. When working at it you don't get time to see the rest of the farm show. For those that don't know, it is the largest farm equipment show in the world and covers 160 or more acres.
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."

JetAonly
Explorer
Explorer
Very interesting! The two Duramax I owned had grade braking, and later models have an exhaust brake. You don't mention what year engine/transmission your used. You might find those features useful.
2000 Monaco Dynasty
ISC350

SoCalDesertRid1
Explorer
Explorer
That is a really great report on your diesel conversion. Thanks for sharing!
01 International 4800 4x4 CrewCab DT466E Allison MD3060
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20' BigTex flatbed
8' truck camper, 14' Aristocrat TT
73 Kona 17' ski boat & Mercury 1150TB
92F350 CrewCab 4x4 351/C6 285 BFG AT 4.56 & LockRite rear

ronfisherman
Moderator
Moderator
Great for follow up reports.
2004 Gulf Stream Endura 6340 D/A SOLD
2012 Chevy Captiva Toad SOLD

EdNdonna
Explorer
Explorer
That's cool. do you still come to the tulare farm show?
2006 Fleetwood Bounder 34H Cat C7 300hp

BigRabbitMan
Explorer
Explorer
EdNdonna wrote:
that's great mileage and the power to go with it. a great combination.
Are you still involved with harvesters? At least I think that's what you use to do.

I was in sales for almond/walnut harvesting, but retired 3 years ago. that is why I had the time to make the long trip!
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."

EdNdonna
Explorer
Explorer
that's great mileage and the power to go with it. a great combination.
Are you still involved with harvesters? At least I think that's what you use to do.
2006 Fleetwood Bounder 34H Cat C7 300hp

BigRabbitMan
Explorer
Explorer
EdNdonna wrote:
I wonder why they are not used in the new Rv,s?

The choice of engine is tied to the choice of frame. About the time that the Duramax had been proved in pickups and light duty trucks, GM got out of the frame business and there is no other independent frame builder of lighter duty frames other than Ford. Ford, of course, will only use their engines. The other factor is cost of a diesel engine vs a gas engine at the 30'+/- price points.

At this point, I have returned from my 8,424.6 mile trip and the fuel mileage to date is 14.2 mpg. I switched the banks tuner to the economy setting for the last 5 tanks of fuel and for those 5 tanks the mileage has been 15.08 mpg. That was from Michigan to Oregon via I-90, I-84 and {-5 most of the way. We will see what it does over time.

Take care,
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."

EdNdonna
Explorer
Explorer
somehow I missed your post.
Its good to hear its doing good.
It's not something I want to do but I always thought those motors would be great in an Rv.And sure can appreciate the time and effort you put into it.
I wonder why they are not used in the new Rv,s?
2006 Fleetwood Bounder 34H Cat C7 300hp

BigRabbitMan
Explorer
Explorer
EdNdonna wrote:
how's the rig doing?

It's doing well! I just went through Tipton 10 days ago (I am originally from the Shafter/Bakersfield area)! I have now gotten back from that trip and am able to give a more complete response.

The following is a report that I just posted on the FMC Owners Club website. It should bring you up to date as it includes a mileage check on flat ground and one in the mountains.

**********
Since I now have just under 5,000 miles on my conversion, I thought that I would do an update.

The first thing to note is that I am very happy with what I call the "drivability" of the coach. I like the ease of merging with traffic at speed, not slowing down for most hills, engine starting in a revolution or two, butter smooth shifting, a 700 mile fueling range, an even quieter interior and other smaller factors. Many people are interested in what my fuel mileage is as that is a significant factor with any motor home. Historically, with the 440 I got about 7.0 mpg most of the time. That is probably about average for an FMC.

As expected, I have seen a significant increase. Since fuel mileage varies with driving style, weather, terrain etc. I decided to do some close measurements under specific conditions to help define what was occurring rather than just post a series of numbers. So on a recent trip to CA I decided to do a flat land test and a mountain test.

The flat land test was from Redding, CA to Bakersfield then back north to Santa Nella, CA. That was a run of 674 miles over three days time. The first half of the trip was with a storm coming in and a lot of cross wind. The second half was with relatively calm winds. I also made five diversionary trips into towns for various reasons so it was not all straight down the freeway driving. I spent most of the time in the truck lane at 60-63 mph as it was a comfortable driving speed and I didn't want to be in and out of the 70+ mph left lane. The net result was that I got 14.7 mpg for that segment of the trip. I was not towing the Subaru Brat.

For the mountain segment, I went from Redding, CA home to Cottage Grove, OR. The beginning and end of the trip were at a similar altitude with an initial gradual climb from Redding to Weed at 3,900 ft. It then dropped down to the Shasta river and back up to 3,000 ft then back down to the Klamath river. Those were 4 or 5 mile 5 & 6% grades after some flat stretches. It then went from the Klamath river down in the canyon up to the top of the Siskiyou pass in Oregon at a little over 4,100 ft which is the highest point on I-5. After dropping down the 7 mile 6% grade into Ashland it became a series of ridge crossing with the first several at the 2,000 ft level then into the valleys in between. As I continued north, the ups and downs became less significant until I reached home in Cottage Grove. Again, I was primarily in the truck lane except when passing trucks on grades. When descending 6% grades, I slipped the Allison 6 speed tranny into third gear (which is the same gearing as second gear in the 727 tranny) and came down the grades at 50-55 mph without needing to use the brakes.

The mountain portion of the trip was 301 miles and the coach got 13.3 mpg which is a respectable number for mountain driving in my opinion.

With those two numbers in mind and the conditions that created them, I expect my long term number to be somewhere in between them. Towing the Brat will probably reduce those numbers by a mile per gallon. Even with this kind of fuel mileage, it will take a lot of miles to recover most of the cost of the conversion excluding the unpaid labor cost for myself and the others who invested significant hours as well.

But, yes, I am glad that I did it and hope to see all of you on the road or at a future rally. Schedule yourself for the June Mega Rally in Carthage, MO and you may have the opportunity to take my coach for a test drive.

*********
There is now a second FMC owner converting his coach to a Duramax with 6 speed Allison. Here is the link to his thread.

In the Rally section of the above FMC Owners Club forum is the information about the June rally. You are welcome to stop by and view the coach and maybe get that test drive mentioned above.
BigRabbitMan
Gas to Diesel Conversion project
76 FMC #1046, Gas Pusher became a Diesel Pusher
Discussion thread on this site
"You're never too old to learn something stupid."

EdNdonna
Explorer
Explorer
how's the rig doing?
2006 Fleetwood Bounder 34H Cat C7 300hp

rgatijnet1
Explorer III
Explorer III
BigRabbitMan wrote:
I thank all of you for your kind comments. It felt great to actually drive it while knowing it was something that I created. And as a bonus, it performed just as I had imagined that it would.


My Son, who is visiting us right now, has that same engine/transmission combo in his 2500 Chevy pick-up. He uses it to tow a 5th wheel. Modifications done to his combo include a 4" exhaust, a cold air intake, and a programmable monitor that allows him to make changes to the engine computer "on the fly" to adjust for various conditions. It is a great combo for your coach. Congrats!