Destination Unknown - a 1997 F350 build

[Eldgen]

I have a 93 cclb, when I built my sliders I used a big section of angle from a semi frame I stripped and double framed the entire thing from front shackle to rear spring hanger then welded my sliders to that. Stiffened the frame up nicely. Then I did a 3 point mount on the flatbed.

 

[SDDiver5]

Nice! I love the OBS Fords!

 

[Chorky]

I bought a 97 OBS Uhaul truck for the box. Decided the extra GVW of the Uhaul would be a bonus. Instead of putting the box on the F350, I am putting the 4x4 running gear on the cab & Chassis.

Is the uhaul frame significantly different from the F350? I figured it would be the same basic frame and supports, only longer...maybe I am wrong?? Even if the frame swap has a higher GVWR than the F350, you are probably still limited by the running gear (axles) - unless you are changing those out also....at which point I wonder how much the driving characteristics will change - especially if the axles and frame add significant weight. I have been following your build thread though, some great ideas!

I have a 93 cclb, when I built my sliders I used a big section of angle from a semi frame I stripped and double framed the entire thing from front shackle to rear spring hanger then welded my sliders to that. Stiffened the frame up nicely. Then I did a 3 point mount on the flatbed.

I have considered something similar but the problem with this I have found is it can cause more problems if not done right. Metallurgy and engineering are pretty important in terms of cad drawings and figuring stress points with specific loads and attachment areas. I have heard of some stories of frame strengthening gone wrong, so I figured I would look at other options before boxing or strengthening the current frame.

Nice! I love the OBS Fords!

Same here! Theres always improvements to be made though.

 

[Motafinga]

Having been down the bad road of a cracked frame I would stay far away from air bags. Just build a proper spring pack or add a mechanical helper spring. An air bag takes the upward travel of your axle and puts it on a bracket attached to the frame where it wasn't designed to take stress. In fact the AB brackets bolt to the thinnest section of frame that has a relief for your shock absorbers. NOT what ford intended

 

[pappawheely]

Is the uhaul frame significantly different from the F350? I figured it would be the same basic frame and supports, only longer...maybe I am wrong?? Even if the frame swap has a higher GVWR than the F350, you are probably still limited by the running gear (axles) - unless you are changing those out also....at which point I wonder how much the driving characteristics will change - especially if the axles and frame add significant weight. I have been following your build thread though, some great ideas!

The axles are the same but the frame on the cab & chassis is taller, has reinforcements, and is made from thicker steel. That's why it has a greater GVW. The F350 is 9200, the C&C is 11K.

 

[GoinBoardin]

C&C frame is narrower out back with straight rails instead of the arch over the axle as well.

 

[Chorky]

Having been down the bad road of a cracked frame I would stay far away from air bags. Just build a proper spring pack or add a mechanical helper spring. An air bag takes the upward travel of your axle and puts it on a bracket attached to the frame where it wasn't designed to take stress. In fact the AB brackets bolt to the thinnest section of frame that has a relief for your shock absorbers. NOT what ford intended
View attachment 416948

Whoah! Interesting!! I was actually planning on bags front and rear to allow for a softer spring (very rough roads), but pump them up when towing or fully loaded on the highway. Now you have me rethinking things...Can you elaborate? How long did it take to do this? What kind of loads where you hauling? On what kinds of roads?

The axles are the same but the frame on the cab & chassis is taller, has reinforcements, and is made from thicker steel. That's why it has a greater GVW. The F350 is 9200, the C&C is 11K.

Ok...that's what I was not sure of. So that being the case I may opt to actually do the same thing knowing it is a stronger frame - which is the one thing I am worried about most. Maybe then the air bag discussion wouldn't be a problem. As is I already plan to overload the truck (with 60 gal of water and 125 gal of diesel plus a quad and a front hitch mounted bike - not even including the camper/storage box and all other sorts of goodies..). Its interesting the axles are the same...makes me wonder if Ford severely underrated the F350 axles. Does your thread talk more about the cab&chassis frame? I'd like to read up more on it - it seems as if we both are looking for a similar end-product/truck.

C&C frame is narrower out back with straight rails instead of the arch over the axle as well.

Hmm...I wonder how this might complicate larger (and a 3rd) fuel tank, and other items.

 

[pappawheely]

Its interesting the axles are the same...makes me wonder if Ford severely underrated the F350 axles. Does your thread talk more about the cab&chassis frame? I'd like to read up more on it - it seems as if we both are looking for a similar end-product/truck. Hmm...I wonder how this might complicate larger (and a 3rd) fuel tank, and other items.

The axles are one ton axles. Dana 60 in front, and the sterling in the rear. Unfortunately my photos were kidnapped by photo#uckit. The frame rails are narrower than a pick-up.

 

[Motafinga]

Yeah I haul an Alaskan Camper in a utility bed with a dirt bike on a hauler sometimes. I only keep fairly light weight items in the ute bed. I do run it off road quite often like this but I firmly believe the frame crack would've never happen without the air bags pushing and twisting on the frame repeatedly. Think of it as taking a stick over your knee...yeah it's kinda like that. The previous owner put them on and I ran them for about 2 years before I noticed the cracks 2 weeks ago. They've been properly repaired and I 'm confident the repair should hold up but I'm running a progressive helper spring going forward.
Just thought I'd pass along my experience to save someone some grief

 

[Chorky]

The axles are one ton axles. Dana 60 in front, and the sterling in the rear. Unfortunately my photos were kidnapped by photo#uckit. The frame rails are narrower than a pick-up.

Yeah thats a shame about your photos. Thank you for sharing! I was bummed to be unable to see the pics on your build thread. So same axles....very interesting. I have a 60 up front and sterling in the rear as well @ 4.10s. But that will likely be changing - and adding some 'fake' lockers. Are you keeping the 10.25 or stepping up to the .5? I like the idea of having the same width front-rear. Have you run into any interesting problems as far as driveline/fuel tank clearance? I'm assuming the exhaust will run on the outside of the frame with the narrower width? How much is the width difference? It does seem to be much more stout....but I wonder about the design of the C-channel supports - theyre quite different than the F350, and obviously due to the design being to support extra weight of movers; however, any thoughts (or have you tested) stress on joining locations (not sure if you've done any CAD inspections). And with the narrower frame, that probably means a difference of stress points on the axles - so I wonder if it would inadvertently cause more stress on the bearings or axle tube, especially with a high weight and larger tires. Haha - sorry for all the questions, it just seems like you've already done the exact homework that I'm currently working on.

Yeah I haul an Alaskan Camper in a utility bed with a dirt bike on a hauler sometimes. I only keep fairly light weight items in the ute bed. I do run it off road quite often like this but I firmly believe the frame crack would've never happen without the air bags pushing and twisting on the frame repeatedly. Think of it as taking a stick over your knee...yeah it's kinda like that. The previous owner put them on and I ran them for about 2 years before I noticed the cracks 2 weeks ago. They've been properly repaired and I 'm confident the repair should hold up but I'm running a progressive helper spring going forward.
Just thought I'd pass along my experience to save someone some grief

So with your bags pumped up on rough roads I'm not too surprised of the crack. I guess I figured they would have been aired down off road to allow for more suspension movement and only pumped up on the highway for stability reasons. Seems to me thats how it should work anyway. I mean the idea of them is to provide some additional support, but when your off road you probably dont want that support and instead want to encourage suspension travel for traction and comfort. Regardless...I certainly appreciate you chiming in!! I am going to look into this more before doing bags.

 

[pappawheely]

Yeah thats a shame about your photos. Thank you for sharing! I was bummed to be unable to see the pics on your build thread. So same axles....very interesting. I have a 60 up front and sterling in the rear as well @ 4.10s. But that will likely be changing - and adding some 'fake' lockers. Are you keeping the 10.25 or stepping up to the .5? I like the idea of having the same width front-rear. Have you run into any interesting problems as far as driveline/fuel tank clearance? I'm assuming the exhaust will run on the outside of the frame with the narrower width? How much is the width difference? It does seem to be much more stout....but I wonder about the design of the C-channel supports - theyre quite different than the F350, and obviously due to the design being to support extra weight of movers; however, any thoughts (or have you tested) stress on joining locations (not sure if you've done any CAD inspections). And with the narrower frame, that probably means a difference of stress points on the axles - so I wonder if it would inadvertently cause more stress on the bearings or axle tube, especially with a high weight and larger tires. Haha - sorry for all the questions, it just seems like you've already done the exact homework that I'm currently working on.

Not sure why you would want to change from 4:10's. With 37 inch tires I still pull off the line in 2nd gear (5 speed). The 10.5 is better I guess but the 10.25 is a fine axle. I am having all kinds of clearance issues with the driveshaft and tank, lol. I am going to have to drop the driveline down to clear it. I must be honest, I spec'ed the fuel tank when I was going to use the F350 frame. I pushed the tank between the frame rails of the C&C to see what it looked like and then couldn't get it back out. It's there to stay now. I am going to run the exhaust to the pass side and then up in front of the door. I don't want the exhaust under the back of the truck at all; too much planned back there. I have not done any cad simulations. I made custom spring hangers to accomplish 2 goals. First, I wanted to get rid of the lift blocks. My Atlas springs mount directly to the axle housing. I also moved the spring pads out to match the width of a pick-up. I wanted the extra width for sway control and in case I ever have to replace the axle. Pick-up axles are much easier to find than C&C axles. I am running a single tire in the rear, so I don't need that clearance. The narrow frame has allowed me to run the shocks, and sway bar outside the frame rails. The real estate inside the frame rails is occupied by the fuel tank and house batteries. I made keeping the center of gravity centered and down low a priority.

 

[Chorky]

Not sure why you would want to change from 4:10's. With 37 inch tires I still pull off the line in 2nd gear (5 speed). The 10.5 is better I guess but the 10.25 is a fine axle. I am having all kinds of clearance issues with the driveshaft and tank, lol. I am going to have to drop the driveline down to clear it. I must be honest, I spec'ed the fuel tank when I was going to use the F350 frame. ....View attachment 417193

I did some calculations and I think with 37's and 4.88's it keeps the same RPM range. I have a slushbox though - considering the 6spd swap. Not that keeping similar RPM's is necessary, especially with the 7.3, but I figure it would be nice for mountain roads. Speed really isn't something I'm aiming for. Although, I will have to re-check the numbers, because with keeping the 4.10 it would allow for lower highway RPM's and a stronger pinion.

That sounds - like it offers opportunity for fab work lol. The pick looks pretty good though! I like your ideas for the sway bar. Did you ever consider using a F700 frame before going the u-haul route?

 

[pappawheely]

That sounds - like it offers opportunity for fab work lol. The pick looks pretty good though! I like your ideas for the sway bar. Did you ever consider using a F700 frame before going the u-haul route?

No, I bought the Uhaul for the box. I took a vow of poverty in order to work remote. Mine is a no budget build.

 

[Chorky]

I took a vow of poverty in order to work remote.

HAHA I know that feeling well! Did exactly the same thing - but for me I actually live in my truck (and trailer) so I guess you could say I have 'extra' money (in the form of what would be spent on rent/mortgage) for a custom truck and future trailer build. Which is the reason to do it right the first time, even if it costs more than desired.

 

[Motafinga]

A frame repair shop I spoke with said they've seen it 3 times already, and some searching turned up several posts of it happening under "normal driving" conditions too. Best of luck though!