I don't know about other areas, but around here, most semi's can lock up all 2 or 3 drive axles. Really don't need front wheel drive when you got 8 to 12 wheels with power to them

 

How many semi tractors go off road? I'm not sure how semi-tractors are relevant.

 

hehe Around here...In the winter.... LOTS of em! Now it may not be intentional...but they try.

 

That was my initial thought that the 4WD would increase fuel consumption. Usually, I agree with the addage best have it an not need it but is it worth the extra fuel consumption over the life if I only use it once (if even). My last truck I only used the 4WD in Kansas during an ice storm. I now live in Texas and do not plan on visiting any state with ice and snow then again the wife may veto that.

So if the 4WD is locked in 2WD then it should not affect fuel economy? Only AWD sees the fuel consumption since they cannot unlock their hubs?

 

Personally, I can't live without 4x4 when towing. I have been caught in blizzards that cut visibility down to 25ft on non plowed roads on numerous ocassions towing our 4place trailer. I would never imagine not having it...

 

LOL, I've been known to do that from time to time in a tight parking lot or drive through. I guess they call that drifting, Alaska style!

 

They're not relative, but for the records I drove a semi dump for over 10 yrs, and did quite a bit of off roading. My KW had diff lockers, and you could lock both rears together for 8 wheel drive. It worked great loaded as long as wanted to go straight... on the other hand it wouldn't move
empty... I could talk all day about trucking...I guess I miss it.

 

Years ago I was working at the same place with a guy who was commuting 35,000 miles a year. He drove small pickup truck and when that got rear-ended he bought bigger one with 4WD.
When I asked him why doesn't he buy econobox for commute, he answer that he needs pickup because of his yard. His yard was 20 feet by 50 feet.
Would he drive econobox, the money he would save over the year would not only pay for Escalade twice a year to haul yard clippings, but also for Jaguar on included Las Vegas vacations.
We all do make our choices.

 

AWD is only on cars and SUVs, not on trucks. Older Jeep Grand Cherokees were gas hogs, and I think that kind of gave the system a bad rep for gas mileage, but yes, connecting more turning parts to the engine will cut down the MPGs.

I don't understand this whole argument that 2wd gets better gas mileage than a 4wd when it comes to trucks though. What exactly about the unit bearings increases resistance so much compared to the 2wd spindle bearings that it causes increased engine loading? When the hubs are unlocked the stub only rotates sympathetically, and the transfer case isn't pulling power from the transmission, so there's no real losses there, at least not enough to suck HP out of the engine. Nothing in the front end is being powered, it's just hanging there. If you wanted to get insanely technical, yeah, I could see maybe a few tenths of a mile per gallon, mainly from the extra 4 sq ft of frontal area that comes with a slight height difference, but finding a $5 bill on the sidewalk would cover the difference in fuel consumption for a month. You lose more mileage per tank with a heavy right foot.

This MPG thing is turning into the "2wd trucks can haul more!" joke, where people think that since the curb weight is lighter on 2wd trucks, and GVWR doesn't typically change inside cab/bed combos, that the extra 250# of hauling capacity is something worth considering when buying a truck. If you need that extra 250# so badly to come in underweight, you should probably be looking at stepping up into another truck, cause on fat Aunt Thelma tagging along could ruin your weekend if you ran into a highway cop.

 

Damn Aunt Thelma!!

 

Until they hit a pothole or a bad stretch of on ramp loop.

 

The thing I don't like about Ford's 2wd Super Duty trucks isn't the strength of the twin i-beam suspension system- it's the fact that the TIB changes camber as the suspension cycles. Much more than a double a-arm front suspension.

Think about the nature of a pickup truck. It sees dynamic loads: unloaded one day, loaded the next. As the rear suspension is loaded due to a trailer's tongue weight or simply by loading a pallet of mulch in the bed, the front suspension begins to unload as the rear is loaded. The front suspension moves upward from ride height. In an extreme case, taking a long road trip could result in some weird tire wear and strange handling.

But air bags or some sort of load leveling solution could fix that.

The TIB suspension is stout. Desert truck get some serious travel out of the basic design. But I've never had much luck with it holding a good alignment back in the mid 90's farm trucks. My front tires always seemed to wear the edges of the tread no matter how tight everything seemed up front.

 

Ford definately screwed the pooch on the steering stabilizer. But a simple dual stabilizer kit solves that problem. You're still left with a better steering set up.

 

With a true 4WD like these, the mpg penalty is much less than an AWD (especially some of those horrible early "shift on the fly" or full time AWD systems in the 80's and 90's) as you are not having to accelerate and spin the front driveshaft, differential, and axles.

But, you do still have:
- The parasitic friction and fluid pumping losses in the transfer case
- Aerodynamic penalties since most 4WD are taller than 2WD
- More weight to accelerate
- Plus many folks with 4WD tend to gravitate towards bigger and more aggressive tires - which come with aerodynamic, weight, and rolling resistance penalties.

Those do add up. From my experiences, it is rarely less than 1 mpg. Usually in the 1 to 2 mpg range.

 

My last truck was a 2000 7.3 F250 2 wheel drive 6spd manual with 3.73 LS differential. I had it for 10 years and had no problems with it on snow or ice on the roads as long as I was careful. The only problems I had were with the 5th wheel hooked up trying to move on wet grass or slightly muddy surfaces; it just would not do it. After getting a tow a few times in those situations I decided my next truck would be 4wd. I've already had a few instances where I used 4wd in this truck with a trailer off road that I would have needed help with the 2wd truck. 4wd is about $3k more than 2wd on a new truck but it's worth it to me.

Mike