Gvwr
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Joined: Mar 2006
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I don't think I'll need to go tandem, but if this is a 350 axle, then I should be able to put duallies on there instead of heavy load tires right? Thanks for the info Dave, I can't believe the wealth of info you have about these trucks. Is there any difference betwwen frames on the 250 and 350 then? To think I considered buying a dodge, but only for the Cummins TD.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
Dual wheels will not fit on a single rear wheel truck.
Dually axle housings are 4" wider than a SRW axle housing is.
All diesel equiped Fords 250 or 350 have the same rear axle, springs and frame if it has a pickup box mounted on it when it leaves the factory.
All trucks that left the factory with a pickup box mounted on them have 37.5" wide frames.
The F 350 is available as a cab and chassis, nothing mounted on the back, it has a 34" wide flat frame behind the cab.
The cab and chassis trucks have the same length axle housing as the SRW pickups do, they can run duals because of the narrow frame.
The spring perches are mounted in a different location on the cab and chassis axle housings since the springs are closer together.
Dually axle housings are 4" wider than a SRW axle housing is.
All diesel equiped Fords 250 or 350 have the same rear axle, springs and frame if it has a pickup box mounted on it when it leaves the factory.
All trucks that left the factory with a pickup box mounted on them have 37.5" wide frames.
The F 350 is available as a cab and chassis, nothing mounted on the back, it has a 34" wide flat frame behind the cab.
The cab and chassis trucks have the same length axle housing as the SRW pickups do, they can run duals because of the narrow frame.
The spring perches are mounted in a different location on the cab and chassis axle housings since the springs are closer together.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
Since the frame is wider, the rear springs are also wider.
The tires will hit the springs, hard.
A single rear wheel axle housing is 53.75" from brake back plate to brake back plate, frame is 37.5" wide outside to outside.
A dually rear axle housing is 57.75" back plate to back plate and the frame also measures 37.5" outside to outside.
A cab and chassis axle is 53.75" from back plate to back plate, but since the frame measures 34" from outside to outside the springs are also closer together by 1.75" on each side.
So the spring perches on the axle are also closer together by 3.5".
That is how a cab and chassis can run dual wheels with a 53.75" long axle.
All 250 trucks have 37.5" frames, and there is a hump over the rear axle in the frame.
All F350 trucks with a pickup box installed have a 37.5" frame and the frame hump over the rear axle.
A board will not lay flat on top of the entire frame rail.
All cab and chassis F350 trucks have a 34" wide frame and the frame is straight from front to back on the top edge.
If you lay a 2x4 on top of the frame rail it will be touch from one end to the other.
The inside dual wheel will lack about 1 inch of being able to bolt up against the drum.
Since you need clearance between the tires and springs, the dually axle is 2" longer on each side.
For about 400 dollars you can buy spacers to run dual wheels on your axle.
But the spacer shifts the wheel center outside the hub center.
That causes the entire load, or most of the load to be supported by only the outside wheel bearing.
Spacers are not bad if you are towing a trailer and want the extra stability of dual wheels.
But if you are hauling the load on the truck, they are not such a good option.
The best option is to find a factory dually axle.
Everything is the same except the axle housing is 4" wider between the back plates and the axle shafts are 2" longer each.
The rest of the parts will swap from one to the other.
The tires will hit the springs, hard.
A single rear wheel axle housing is 53.75" from brake back plate to brake back plate, frame is 37.5" wide outside to outside.
A dually rear axle housing is 57.75" back plate to back plate and the frame also measures 37.5" outside to outside.
A cab and chassis axle is 53.75" from back plate to back plate, but since the frame measures 34" from outside to outside the springs are also closer together by 1.75" on each side.
So the spring perches on the axle are also closer together by 3.5".
That is how a cab and chassis can run dual wheels with a 53.75" long axle.
All 250 trucks have 37.5" frames, and there is a hump over the rear axle in the frame.
All F350 trucks with a pickup box installed have a 37.5" frame and the frame hump over the rear axle.
A board will not lay flat on top of the entire frame rail.
All cab and chassis F350 trucks have a 34" wide frame and the frame is straight from front to back on the top edge.
If you lay a 2x4 on top of the frame rail it will be touch from one end to the other.
The inside dual wheel will lack about 1 inch of being able to bolt up against the drum.
Since you need clearance between the tires and springs, the dually axle is 2" longer on each side.
For about 400 dollars you can buy spacers to run dual wheels on your axle.
But the spacer shifts the wheel center outside the hub center.
That causes the entire load, or most of the load to be supported by only the outside wheel bearing.
Spacers are not bad if you are towing a trailer and want the extra stability of dual wheels.
But if you are hauling the load on the truck, they are not such a good option.
The best option is to find a factory dually axle.
Everything is the same except the axle housing is 4" wider between the back plates and the axle shafts are 2" longer each.
The rest of the parts will swap from one to the other.
Senior User
Joined: Mar 2007
Posts: 224
Likes: 0
From: San Jose , ca
Dual wheels
Originally Posted by Dave Sponaugle
Since the frame is wider, the rear springs are also wider.
The tires will hit the springs, hard.
A single rear wheel axle housing is 53.75" from brake back plate to brake back plate, frame is 37.5" wide outside to outside.
A dually rear axle housing is 57.75" back plate to back plate and the frame also measures 37.5" outside to outside.
A cab and chassis axle is 53.75" from back plate to back plate, but since the frame measures 34" from outside to outside the springs are also closer together by 1.75" on each side.
So the spring perches on the axle are also closer together by 3.5".
That is how a cab and chassis can run dual wheels with a 53.75" long axle.
All 250 trucks have 37.5" frames, and there is a hump over the rear axle in the frame.
All F350 trucks with a pickup box installed have a 37.5" frame and the frame hump over the rear axle.
A board will not lay flat on top of the entire frame rail.
All cab and chassis F350 trucks have a 34" wide frame and the frame is straight from front to back on the top edge.
If you lay a 2x4 on top of the frame rail it will be touch from one end to the other.
The inside dual wheel will lack about 1 inch of being able to bolt up against the drum.
Since you need clearance between the tires and springs, the dually axle is 2" longer on each side.
For about 400 dollars you can buy spacers to run dual wheels on your axle.
But the spacer shifts the wheel center outside the hub center.
That causes the entire load, or most of the load to be supported by only the outside wheel bearing.
Spacers are not bad if you are towing a trailer and want the extra stability of dual wheels.
But if you are hauling the load on the truck, they are not such a good option.
The best option is to find a factory dually axle.
Everything is the same except the axle housing is 4" wider between the back plates and the axle shafts are 2" longer each.
The rest of the parts will swap from one to the other.
The tires will hit the springs, hard.
A single rear wheel axle housing is 53.75" from brake back plate to brake back plate, frame is 37.5" wide outside to outside.
A dually rear axle housing is 57.75" back plate to back plate and the frame also measures 37.5" outside to outside.
A cab and chassis axle is 53.75" from back plate to back plate, but since the frame measures 34" from outside to outside the springs are also closer together by 1.75" on each side.
So the spring perches on the axle are also closer together by 3.5".
That is how a cab and chassis can run dual wheels with a 53.75" long axle.
All 250 trucks have 37.5" frames, and there is a hump over the rear axle in the frame.
All F350 trucks with a pickup box installed have a 37.5" frame and the frame hump over the rear axle.
A board will not lay flat on top of the entire frame rail.
All cab and chassis F350 trucks have a 34" wide frame and the frame is straight from front to back on the top edge.
If you lay a 2x4 on top of the frame rail it will be touch from one end to the other.
The inside dual wheel will lack about 1 inch of being able to bolt up against the drum.
Since you need clearance between the tires and springs, the dually axle is 2" longer on each side.
For about 400 dollars you can buy spacers to run dual wheels on your axle.
But the spacer shifts the wheel center outside the hub center.
That causes the entire load, or most of the load to be supported by only the outside wheel bearing.
Spacers are not bad if you are towing a trailer and want the extra stability of dual wheels.
But if you are hauling the load on the truck, they are not such a good option.
The best option is to find a factory dually axle.
Everything is the same except the axle housing is 4" wider between the back plates and the axle shafts are 2" longer each.
The rest of the parts will swap from one to the other.
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