My 89 F-450 gets 10-12mpg the truck has a 5spd with 5:13 axle gears the truck tops out at 100km/h 62mph thats on flattest stretch of highway usually the truck struggles todo 80km/h (50mph). The truck weighs 7800lbs so its fairly heavy you gross the truck to 15,000lbs shes really slow.

I'am happy with 10-12 mpg I had a 88 F-450 with a 460 it only got 6-8mpg that was disgusting the truck had good power thou.

A diesel needs gears to get the rpms down a 3spd automatic isn't enough gears it maybe alright for a gasser that is designed to rev and stay revved. A IDI engine likes to pull the best in the 2000-2500 range keeping it closer to 2000 is better. I like to keep it 2000-2200 I kinda wish I had a taller gear than 5th (od) those 5:13s are real speed killers I would actually like to have a splitter. Myself I can't swap the gear to anything taller than 4:63s the old IDI wouldn't have the power to support the 15,000 gvw.

As for putting a dump bed on a Dodge the chassis may not beable to take the stress Dodge wasn't known for strong frames. You better put a good subframe for the deck to sit on so it takes most of the stress.

 

Kenworth, that is 4 tons of rock in my bed, gross was a tad over 16,000 and I have 3.55's in it with a 4 speed. Handles the WV mountains just fine with that setup and loads. Gross over 20,000 when I pull our lowboy and mini excavator or skid steer loader.

 

rpm is were its at with my ats turbo 7.3 idi.i have 3.55 gears and a 4 speed.If I drive 75 i get 13-14, 65 mph 15-17,under 60 20 and up. load does not realy make a diffrence mabe 1mpg.

 

Dave you sure put some heavy loads on your truck I'am surprised nothing has broke or bent a axle you would never beable todo that with a Dodge

For me I get worried about braking power one of the reasons why I haven't gone to a F-350 4x4 I know I can beef the suspension up to carry some good loads. I may still end up converting a F-Superduty into a 4x4 I may try a lockright in the diff first.

My current truck doesn't have any problems climbing the hills it doesn't climb them fast. I would like to have more road speed with less rpms when I do 100km/h (62mph) the revs are close to 3000. The other problem I have is with 5:13s 4th gear will peg the engine so if I try pass somebody 4th gear is topped out at 60km/h (37mph) at 3000. So I have to run it to the peg in 4th then quickly shift to OD to bring the rpms down. The most important gear in my truck is 5th (od) if I didn't have it truck wouldn't go any faster than 37mph.

 

Kenworth.
The Loc Rite is not a good thing under a heavy load. As far as that goes I do not think any locker is a good idea when the weight is on the truck bed. Something has to give when you go around corners, and it will be one of three things that break.
1. The bolts that bolt the axle to the hub.
2. The wheel studs.
3. The axle.

I tried a locker, it was great.
Then I installed a dump bed and it was a nightmare.
I now run a limited slip, I am happy again.
The locker went better, but it caused to much stuff to break.
I broke 1 and 2 regularly, thank god I did not break #3.
Locker finally disinigrated, cost right under a grand to replace everything it took with it and labor to fix it all.

Basicly I had a axle housing, two axles and a yoke for the u-joint, everything else was trashed with metal fragments.

I can not imagine driving with any lower gears than I have now, unless I had an overdrive tranny and also an auxiliary overdrive unit.

That is a thought, if you put an overdrive unit in your truck, when you hit overdrive, then you could flip the auxilary overdrive on and run like you had 4.10's and your 5 speed. You would also have 10 forward gears and two reverses. Best of both worlds and bunches of gears for dragging things around.
The double overdrive would get you close to 60 at 2000 RPM.

 

I do trust what you say Dave I seen the pictures of the weight you haul so if you are breaking axle shaft bolts etc the same thing will probably happen with me. That is one of my concerns about breaking the rear end sure its a Dana 80 but when you have 6000lbs on it plus you have 4 tires on the back scuffing on the ground. Something does have to give when you have that much weight its easy to break something.

The other thing I'am worried with a locker the tires have to be equal diameter well how is that going to happen when you have a offset load on the truck so one set of tires is squating more than the other. Non of the loads I haul are equally distributed on the deck of the truck I usually like to load the driverside of the truck slightly heavier than the passenger side.

I have had the offroad guys tell me a locker will not give any adverse affects etc but I don't think they realize what a heavy loaded truck is like. Even with a open diff the rear duals scuff like crazy when turning sharply on pavement with a heavy load. Some of the loads I carry weigh more than most 1/2 ton P/U trucks.

As for the gearing I'am living with the 5:13s it gives poor fuel mileage but the slow speed pulling power is good there is no excessive clutch riding moving around. I like to beable to fully disengage the clutch before putting the power to it when loaded backing up or climbing a driveway with a load. I never slipped the clutch once the old IDIs do have the torque in the lower rpms

When I go through one of the school zones which is one of the main roads through the community hub I can go through the school zone at 30km/h (16mph) with a empty truck in OD and the engine reving at 1100 rpm

 

Kenworth, I got a good laugh out of the school zone in OD. You just got that rear gear so you do not have to shift gears.

The load to one side or the other never caused me problems.
What was a problem was going up steep hills and having to turn the truck.
Dirt or gravel was usually OK because it could slide/slip a tire so it would turn.
Blacktop or concrete was a nightmare, turn the wheel and the truck went straight, front tires just slid straight ahead. To turn right I drove as far as I could straight, stop turn the wheel left and back up, straight wheels and go forward, stop turn wheels left and back up. You get the idea. Talk about a strain on the truck taking off from a stop with a load on a steep hill bunches of times so you could make a sharp turn.
The locker is great when the load is not on the rear axle or the truck is empty. That locker was the best thing for plowing snow that I ever had. It was great for off roading. But for work hauling stuff in the truck bed I wish I had never seen one.

You talk about the tire scuff when the are 14" apart then multiply that by 7 to get to the other side of the truck. Sometimes when I did a shallow turn and then the road straightened out, when the locker unlocked it sounded like a freight train took the whole back of the truck off. Bang, no I meant BANG, it shook the whole truck. Scared me to death the first time it happened, I was sure I had broken an axle or worse.

 

Thanks for the reply you answered all the concerns I had I think I will stick with a limited slip or a open diff. A landscaper friend of mine has a older Chev 1 ton dually with a 10' dump his truck seems to walk out of the same driveway I have problems with. I don't know if its he is running better tires or its his truck isn't as front heavy as mine. His truck probably flexes better than mine being his truck has 2wd A arm suspension. My old F-450 with a solid front axle and leaf springs the front end doesn't flex much.

I did have the same problems with my 1980 F-350 dually with the same 12x8 deck. I had the bandag CTD recaps on the drive tires of that truck too maybe the retreads are causing the problems http://www.bandag.com/products/north...actionDeep.jpg

The retreads are 130.00 per tire compared to 180-200 for new traction tire like M-55 Toyo.

 

Go limited slip. It has clutches so it can turn OK with the load on it. It does not go as good as the locker, but it is way better than an open differential. I am off road in mud so much that I run mud tires at 250 a pop year round. All the highway driving I do chews them up, but at least I do not have to worry about getting stuck on a job somewhere in the middle of nowhere. Since I am in excavation and site prep, I have to go there hauling materials before there is a site or roads. Last time I got stuck she was in up to the headlights, and the passenger side west coast mirror was almost dragging the ground. Took a 977 Cat crawler loader to get to the truck and pull it out.

 

hey dave and kenworth what about the ARB air locker? i know that means another thing to add to the engine compartment as far as the compresor,air tank and such. but if your in daves business or mine(mechanic),it might not be a bad thing.
also there is the option of that new electric locker that should be a good deal.
anyway back to the original topic of fuel milage,my 92 f-250 4x4 3.55's e4od with banks intake and exhaust gets about 18 - 20 in OD . i have never really checked it in just direct(3rd) and empty,because i'm usally towing somthing when i'm in direct and fuel milage goes out the window anyway. i really dont like to use direct lately with fuel prices being what they are $2.40 i paid last week,$2.33 this week,cant see how those truckers can be making a living the way things are.

 

The ARB is good myself I don't know if I would trust it all these differential traction aids are for empty trucks nothing with heavy loads on them. The ARB works like a spool offroad both wheels are locked together so you really wouldn't have any steering. A ARB would probably work alright in a 4x4 where the front wheels can pull the front end to the direction you want togo.

I have a 2wd 89 F-450 if the truck was a 4x4 I wouldn't worry about a traction aid. The older first version of the F-450 (F-Superduties) are all 2wds so which most 1 ton dually cab and chassis trucks are. You don't find many LWB 4x4 F-350s or Chev 3500s.

I'am in mud and goo as I'am in the construction/excavation/landscaping industries working in construction sites and landclearing etc. I try to avoid the deep mud I have been into places where the truck sinks in 6-8"s where I have to fight my way though it. I mainly get stuck in loose gravel where the tires spin on top the tires don't dig they just spin. It maybe the tires I have on my truck are too highway/oriented and maybe have togo to something more aggressive.

 

There is also the OX locker, kinda like an ARB but cable actuated. Dont know if they have very many applications available yet though.

 

I would go with a selectable locker. this means its an open diff when ya want it to be and at the flip of the switch the diff is locked in. there the absolute best for trucks that get used with heavy loads. most 18 wheeler cabs come with them standard as well as most agriculture tractors. i but an arb in my truck and its the best. when ya go around a turn ya just disengae the lcoker. i only use it when iam going straight and need the extra traction. my truck is a farm truck and it sees some awful heavy loads. ive never had a problem with it yet. i think ya guys were running the lockers that lock in when the feel a wheel spin. in my opion its about the worst thing ever made. they alwasy seem to lock in when ya dont want them to and turning with a diff locked is alot of strain on the whole truck. dually or not.

 

The ARB is made for the Dana 80 with 37spine shafts just the price is a bit scary for me I'am looking at 1500 dollars CND plus installation.