Axle alignment

[Acoals]

I have a older Ford L9000 with Rockwell rears on Hendrickson Walking Beams. The rears sit offset each other slightly. It seems that the back axle is the one that is out, as the tires sit about 3/4" farther away from the frame on the driver's side than the passenger side. Comparing the two axles they are about 1" offset from each other.
The truck has been this way for the three years and probably about 15,000 miles I have had it, aside from noting it in the mirror on the road the truck dog tracks a little, or at least appears to in the mirror in reference to the lines on the road and the trailer.
I replace the transverse torque rod on the forward axle last year, and the offset seemed to improve a little, maybe 25%. I am going to be replacing the rest of the torque rods now while I have the body off.

What would cause this? Some of the torque rods are rough, but I don't see them pulling the axle far enough to make much difference, unless the lengths were changed.
Is the issue in the walking beam bushings? The axles don't really shift side to side much when loaded and turning.

 

[Tyler d4c]

Does it have the rods from the frame rail to the top of the diff. Early ones didn't.

 

[Acoals]

There are 2 torque rods per axle, four in total. One runs longitudinally from the axle to the crossmember, and one transversely from the top of the axle to the frame rail.

 

[crane operator]

Could be walking beam bushings. Could be wheels. Let me guess- its dayton wheels?

 

[Truck Shop]

Different axle housing--the main beam hangers/welded to the housing were set up on a different
suspension/truck or the housing was changed at some point and was not lined up correctly.
would not be the first time that's happened with walking beam.
*
But what do I know----------I'm just a new age OTR mechanic. To work on dumps you have to
work in the dirt.

 

[Acoals]

Could be walking beam bushings. Could be wheels. Let me guess- its dayton wheels?

Yes, it has Dayton wheels.

 

[Acoals]

How would one decide whether or not it is the walking beam bushings? If it was not the bushings, but a different axle housing or other problem, what would be a solution?

If I put a longer torque rod on the back axle, would that push the axle over, or would there be other alignment problems?

 

[grandpa]

I doubt its the bushing, when they get loose the tires will actually rub on the spring shackles.

 

[Truck Shop]

Pretty friggin hard to ware out the beam bushings with a four torque arm suspension.
It's the reason those were installed. Real common on trucks that run allot of asphalt/
inner city-garbage rigs. If distance is same from axle center to center both sides plus
no abnormal tire wear leave it. Measure distance from edge of drum to outside hanger
on one side.

 

[Truck Shop]

How would one decide whether or not it is the walking beam bushings?

And to answer that-leave both lateral torque arms off-turn hard both directions. Lateral torque
arms cut the ware on beam bushings by 65%.

 

[Acoals]

Lateral torque arms cut the ware on beam bushings by 65%.

That explains why the lateral arms are so worn out as opposed to the longitudinal arms.

 

[Truck Shop]

That explains why the lateral arms are so worn out as opposed to the longitudinal arms.

Correct--in some cases I've seen were used in extreme rough road conditions the top
torque arm bracket for lateral arm support--where it's welded to axle housing cracked
all the way around, or where mounting bracket is bolted the frame rail with major
cracking. Allot of pressure exerted on those two points, but those were also trucks
that were rode real hard & put up real wet.

 

[Acoals]

I am just going to replace the torque rods and call it good, I am not tearing the walking beam apart this year.
I did notice that the wheel spacer on the left rear axle is different than the others, it's wider, and makes it appear to be out of alignment more than it is on that side. I will see if I can find one that matches on my parts truck in the weeds.