Where to put steering box for my 5 ton-based truck

[Trango]

Hi all,

Years ago (2009-2010), I blew apart my M35a2 and combined parts from it, a few 5 tons, and a civvy Ford medium duty to make a hybrid truck.

I stuck a Ross Hydrapower box outside of the driver's side frame rail, and used it to drive a longitudinal drag link against the stock 5 ton axle steering arm.

It worked very well, although I experienced some minor rubbing against the bottom of the pitman arm on full lock.

Fast forward to 2022. To take advantage of the better availability and weight capacity offered by the Michelin XZL tires being surplused these days, I recently swapped out all of my old, aging Michelin XL 48's to the new 53's. Unfortunately, the light steering rubbing issue that I had with 48's is now fairly painful with 53's.

I put together this video. For me, the right answer is to move the steering box up on the frame rail, using an extension plate if necessary.

I'm concerned that this will create too much angularity with the drag link, causing bump steer. I'm also wondering if I'm missing anything. Thoughts?

Thanks in advance.

 

[Trango]

For reference, with the drag link disconnected, here is the interface between tire and the steering arm rotated as far out of the way as it will go. This was done for diagnostic purposes only.

 

[Trango]

Another shot, of the current interference

 

[Trango]

Gratuitous oblique shot

 

[smoke]

There was another member that was have similar problem with m923 truck when switching to 53s. I remember talk of a different rim style to offset tires out just a little more to get more clearance on pitman arm. I just dont remember which rim style other members told him to go with. Other idea, move steering box back toward axle at same level found short drag link 4 it. Run it ( drag link) in board toward frame side lengthen the knuckle attachment so the drag link can run frame side of box. My 2 cents.

 

[Jbulach]

HEMTT wheel… helps a bit over a combat wheel.

Yes, move the steering box straight back as far back as you can still make your input shaft work. Also clock your pitman arm counter clockwise so that it’s 90 degrees to the drag-link while wheels are straight.

 

[Jbulach]

Your drag-link looks fairly long, just for ideas… M939a2 right at 20” long.
Also, my box does sit better than half way above the frame with a gusseted piece of angle on top of the frame, as well as a crossmember directly behind, inside the frame.

 

[Trango]

There was another member that was have similar problem with m923 truck when switching to 53s. I remember talk of a different rim style to offset tires out just a little more to get more clearance on pitman arm. I just dont remember which rim style other members told him to go with. Other idea, move steering box back toward axle at same level found short drag link 4 it. Run it ( drag link) in board toward frame side lengthen the knuckle attachment so the drag link can run frame side of box. My 2 cents.

Thanks for the thoughts. I did find this similar post, which describes the same problem on an M813.

I think I'll do a variation of your suggestion. I appreciate your post!

 

[Trango]

HEMTT wheel… helps a bit over a combat wheel.

Yes, move the steering box straight back as far back as you can still make your input shaft work. Also clock your pitman arm counter clockwise so that it’s 90 degrees to the drag-link while wheels are straight.

Your two posts are so incredibly helpful. Thank you for taking photos of your setup. First off, that gusseted plate to elevate your steering box is very much in line with what I would build for mine if I decide to elevate the box. Secondly, knowing that a 20" drag link is an acceptable length, I'll reconsider my previous aversion to simply moving my box aft (rearward) on the frame. Doing this might be easier and provide a cleaner solution.

Something tells me my arms are going to get quite a workout soon, trying out different positions to relocate the box....

Thanks everyone for the help and the effort. This has been of valuable assistance to help me imagine a successful solution.

 

[silverstate55]

Good to see you back on here Trango!

 

[smoke]

I'd suggest a soldier b to help save your arms and or maybe use a pipe and chain loop to hold at height. Than you can maybe slide it back to desire spot. If you have some heavy ratchet straps, wrap the strap around the steering box and the frame tight enough that it dont fall but still let you slide the box back to where you want it. Than tighten strap up to hold it there.

 

[Trango]

Good to see you back on here Trango!

Thanks! I hop on every now and then to see the goings on. It's awesome to see this place so vibrant!

 

[Trango]

I'd suggest a soldier b to help save your arms and or maybe use a pipe and chain loop to hold at height. Than you can maybe slide it back to desire spot. If you have some heavy ratchet straps, wrap the strap around the steering box and the frame tight enough that it dont fall but still let you slide the box back to where you want it. Than tighten strap up to hold it there.

Good thinking! Those steering boxes are deceptively heavy.

 

[smoke]

Any updates? Did you get your box moved back?

 

[Trango]

Any updates? Did you get your box moved back?

Not quite yet. It's been pushed back in favor of other pursuits, and the 10" of snow we got on Friday meant this weekend was a no-go.

I'm hoping to get this done in the next month or so. When I hit end-of-job, I'll report back with pictures!

 

[Trango]

Any updates? Did you get your box moved back?

I finally got around to this over the New Year's. I had a free day, I was sick of having a truck I couldn't drive, and I did a ton of measurements, and realized I could move the box forward a few inches and get the necessary clearance. It didn't put the Pitman vertical at straight ahead driving, but it does allow for lock-to-lock steering without the tire rubbing on anything.

I opted to do this versus putting the steering box back because I was worried about interference with the air brake systems, and what happens during articulation etc. Putting the steering box farther out mostly eliminates those concerns, and actually should result in less potential bump steer since the drag link is about the same length as half of the leaf up front.

The daytime pic with snowy background is of the pitman at full right lock. This should be plenty of room.

Also: in 2wd, with an unloaded bed, a single 53" XZL offers terrible snow traction.