Long distance " Sweet Spot" M35A2

[Oilleaker1]

My Dodge 12 valve P pump Cummins gets 19 MPG at 65 MPH and 2000 RPM. At 70 -75 it drops to 12 MPG. That includes pulling a trailer. So, besides putting on lockout hubs, what is the " Sweet Spot " for a Deuce to maximize your MPG? I've been told they get around 8 MPG stock. Up to 13-14 with hubs and driving them right. I've driven mine all day on fun trips, but never had the chance to check the mileage. I'm planning a trip this summer in it and am thinking about the cost. The Sweet Spot I'm refering to is Engine RPM. Is it the same as the Cummins, 2000?????????? You guys with bad backs and sore behinds know this right?

 

[WillWagner]

If you own a deuce, the last thing to worry about is fuel consumption If you travel on flats. they are comfortable at around 42 around 2000, that doesn't cut it on the hwy though. Most of the time you'll be at close to rated and any hill will require a downshift...or two...three... and the engine will again be around rated RPM. With that said, when I have kept track of the mileage it has been around 8.

Oh yeah, when you refer to "sweet spot" you are talking newer technology where peak torque is at a much lower point in the fueling curve than the peak HP. These are old school, HP and torque are much closer together than new technology.

 

[doghead]

There is a chart in the troubleshooting the LDS TM, it shows peak torque, HP and fuel rate(consumption).

 

[stumps]

There is a chart in the troubleshooting the LDS TM, it shows peak torque, HP and fuel rate(consumption).

Here's a copy.

-Chuck

 

[Bill W]

With my first deuce, 52mph seems to be the sweet spot to where I get 10mpg on the highway. If I was to take one on a 990mile trip again ( NOT!) I would pull the intermediate driveshaft connecting to two rear diffs and I'm sure milage would increase

 

[Josh]

I normally get a week or 2 out of a 55gal drum of WMO. I messure my fuel consumptions in DPW, Or Drums Per Week.

That said, I think I get about 8-9mph running 52-55 on the freeway, and about 6-7mpg If im pulling 8k behind me with some extra in the bed.

 

[davidkroberts]

Ive gotten by best performance on longer trips..... Birmingham to northwest Tennessee at about 2300 RPM which matched to about 52ish mph on stock tires. That being said that was reading the military gauges which have been known for being off a bit. That was the speed i thought i was getting a reasonable road speed without over reving the engine. I think your mileage will be much better if you pull one of the rear axles and switch to lockout hubs. A few minutes with some handtools will save you big money at the pump on a long road trip.

 

[Oilleaker1]

Thanks much for the chart guys! Experience is the best indicator, but the chart made alot of sense since it shows fuel consumption like a constant hole draining. The torque , and HP show about the same thing my Dodge Cummins showed me. 1800 - 2000 RPM's would be a good range to hold it in on the flats which equals about 40-45 MPH. Spinning it up to 2500 RPM's is a waste other than about 5 MPH. Hubs are a definate. The intermediate shaft had never crossed my mind though. Correct tire pressure also. It will probably take me 5 years of driving to pay for the hubs, but the wear/vibration factor is the big plus. The end result seems to point to the fact that you will plan on carrying a fat wallet to fill the tank. Fun = $ , education is expensive, good physical body movement to limber the joints, see the sights, attract hot chicks, AKA chick magnet, well, maybe ---------- John

 

[jblack6527]

One thing, if you're thinking about running on one rear axle, it's a much better idea to pull an axle from the front tandem than to pull the intermediate shaft. With the d-shaft out, the truck will want to spin on take offs if the conditions are less than absolutely perfect.

 

[stumps]

One thing, if you're thinking about running on one rear axle, it's a much better idea to pull an axle from the front tandem than to pull the intermediate shaft. With the d-shaft out, the truck will want to spin on take offs if the conditions are less than absolutely perfect.

Absolutely correct!

To anyone that is confused about that, think about what your car does when it suddenly accelerates: The front lifts up, and the back hunkers down. This is because the center of mass is above the wheels, and the wheels are trying to run away from the center of mass.... that makes them rotate around the center of mass.. The tandem axle does the same thing. When you accelerate, the front axle of the tandem lifts, and the rear axle of the tandem hunkers down.

Where possible, it is always better to put your power into the rear most set of wheels....Which, naturally, is why all the new cars are front wheel drive... sigh!

-Chuck

 

[Bill W]

I thought we were talking about highway driving not cross country becuse CC driving is the only way any of this would be a issue. Short of pouring cloraxx under the tires ( or iced road ) I seriously doubt you could get the deuces tires to spin on a prepared surface even with the intermediate shaft out. I've known several people that have pulled the intermediate shaft and they never bragged about spinning tires. Pulling either of the two rear axle shafts would be quicker than pulling the drive shaft but what would you use to cover up the now exposed hub

 

[glcaines]

My M35A2 is a 69 Kaiser Jeep with a D turbo. I routinely get 10-12 mpg on the highway when I drive it very conservatively. I try to maintain 52 mph as the vibrations seem to fade at that speed.

 

[jatonka]

If you buy a set of lockout hubs for the front axle, and install the 2 drive flanges that you had to remove to install the lockout hubs, on the forward tandem rear, you will change to behavioral characteristics of you truck a lot. And, your fuel consumption will go down. And, your front tire wear will decrease. And your truck will steer a bit easier. And your front axle parts will last longer. You will never see 14-15 MPG with a full size Deuce. I averaged around 10 MPG on the trip across America on Rt 20 3 years ago, in an M109A3 with my lockout hubs and disabled front tandem, pulling an M195A2 with Clothing repair Shelter in it with 3 people's gear and fuel and water and parts in it. 7000 miles, 3 Mountain ranges X2 and I was real happy with 10MPG. check my website for hubs

 

[Deuce_and_a_Half_Dragon]

Okay, so I've heard quite a bit about the lockouts, and pulling an axle shaft. I'm not sure about how the lock outs help??? Do you run with them open or locked in? And I would assume with pulling the axle shaft you would pull the passenger side as that is the powered one, correct?

 

[dragonwagon]

My M35A2 is a 69 Kaiser Jeep with a D turbo. I routinely get 10-12 mpg on the highway when I drive it very conservatively. I try to maintain 52 mph as the vibrations seem to fade at that speed.

I was starting to think i was the only one , mine runs 12 mpg too . That was pretty flat road 50 -52 mph as well .

10 mpg on hilly areas . Hills not mtn . Mi dont have mtn's .

 

[glcaines]

Okay, so I've heard quite a bit about the lockouts, and pulling an axle shaft. I'm not sure about how the lock outs help??? Do you run with them open or locked in? And I would assume with pulling the axle shaft you would pull the passenger side as that is the powered one, correct?

If you are talking about highway driving, pulling the connecting shaft between the two rear differentials will not cause any difficulties involving traction. This is very easy to do. Running lockouts on the front means that when the lockouts are 'out' , you are not spinning the front differencial when the front axle is disengaged. You would only run the lockouts engaged if you need the front axle to engage.

 

[mudguppy]

Okay, so I've heard quite a bit about the lockouts, and pulling an axle shaft. I'm not sure about how the lock outs help??? Do you run with them open or locked in? And I would assume with pulling the axle shaft you would pull the passenger side as that is the powered one, correct?

two options:

1. pull the axle shaft out of the intermediate axle and replace with a front hub (just to cap the hub and seal the axle).
2. replace one axle shaft in the intermediate with a double-splined axle shaft and install a lockout hub, run in 'free' position.

in either option, power is transmitted through to the rear axle. since the intermediate axle is either missing the axle shaft or one side is 'open', then power is not effectively transmitted to the wheels on either side (because of the 'open' differential); thus the same is true for bind and scuff - the wheels of that axle cannot bind and, therefore, do not negatively rob power while driving. it would be like dragging around and extra set of wheels.... well, it is.

it doesn't matter which side you choose. i would choose the driver's side to install a lockout hub so i don't have to walk all the way around the truck to engage/disengage the intermediate axle hub.

however, if i were to use the 'shaft pull' method, i'd do it on the passenger's side - that way if i ever had to do it on the side of the road then i would be away from passing traffic.

 

[maddawg308]

On the highway, I run about 54 mph at 2400 rpm. I don't pay attention to the fuel consumption much, it's gonna be crappy at any speed. I instead run 50/50 diesel and whatever else I throw in the tank. It may not be straight diesel, but it's cheaper due to the nature of the other 50% that is free/cheap.

And to those Prius drivers out there, munching your granola and in great need of a bath:

STOP COMPLAINING, IT'S GREEN.

 

[rosco]

I went through all that milage stuff a long time ago - the so called efficiencies were not measurable. That coupled with the fact that about when you want to change back to max traction, you will be stuck in a rain slick clay mud hole, convinced me that the difference in milage, real or imagined, was of no significant consequence.

If you want better milage, keep it right about 50 MPH.

 

[USAFSS-ColdWarrior]

In our experience over the first 1500 miles of ownership with almost ALL driving being considered "CITY" in the 0-40 MPH range, we averaged 10.019 MPG on straight Murphy USA (Walmart) Diesel Fuel WITHOUT ANY ADDITIVES.

Mileage was checked pretty accurately over that time, and it DID include numerous start-up warming AND pre-shutdown cool-down IDLE TIMES. Also included in that 1500 Mile "test" was THREE Parades with 45 minute "granny-low" creeping and approxiimately 5 hours of combined time at IDLE (0-mpg periods) during parade staging. (The old "hurry-up-and-wait process)

Also factor into this is that we are in relatively FLAT west Texas so downshifint for climbing is RARELY a necessity.

Our deuce's most recent "priior life" was as a Fire-Truck, and the engine is adjusted for some EXCELLENT performance.

Hope this input helps.