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My winter ‘54 3100 task list includes leveling the (box. ). ––-Edit- meant CAB not box.–- Eyeballing and measuring tells me that the port side forward is 1/4 - 3/8” low. My seats and fuel tank are out of the truck ; the time is now.

I loosened the upper fasteners on the port side shackle assembly in preparation for fabricating shims and noticed that the relationship between the shackle side plates and the channel they mate up to is different than that on the starboard side…. On the starboard side there is clearance between the upper ends and the channel the assembly mates to whereas on the port (low) side those shackles ends are tucked slightly up into that channel. Further observation made it obvious that the 2 shackles are dissimilar. I think the low side one is aftermarket and the other one is original equipment. It would make no sense to buy 2 dissimilar replacements so I don’t know what else to think.

I believe that this explains why the CAB is not level. I was not in the shop the day the box cab went on a year and a half ago; I’ve spent a lot of time under that truck since , but never compared the 2 mounts before.

Should be an easy fix. If anyone can shed light on the origin of those two mounts I’d appreciate it , for the sake of my curiosity and understanding.
The lightly rusted assembly is on the low side, note the better clearance of the upper ends on the darker greasy one.

CORRECTION–- I misspoke regarding BOX vs CAB.
I am leveling the cab. Will edit and correct.
Sorry for the confusion. Soft brain.

The greasy one looks like the inner rubber bushings are swollen and disintegrating from the oil the dry one looks like the rubber is not there and looks a little lower we’re the bushing and pin go through .the two look the same ,maybe there already is a shim on the one side .I would take them off to replace the bushings and check the bolts for wear..Carefull taking them apart I think they are fine thread and may need some soaking .

I'm confused, are those shackles for the cab only? how could that affect the level of the box? Every truck I have been under, the box is bolted directly to frame members or sleepers clamped to frame members.

I am with 78buckshot - the bed being lower on one side than the other is likely the wooden blocks or the cross sills (or both) are going away.

Sorry for the confusion- my brain juxtaposed BOX and CAB.
I am leveling the cab , not the box. Edited accordingly.
Getting so I hardly know myself anymore.

Just for my knowledge, what is a sleeper , as referenced by 78buckshot?

"Sleeper" -- On many old medium duty trucks you will find heavy timbers U-clamped to the frame rails, they would run parallel with the rail on top. Then the bed, box, platform would be built on those timbers. I don't know if that is the correct conventional terminology for what I was calling "sleepers."

X2 on the shackle bushings. They definitely need to be replaced.
The greasy side looks to be worse. May be metal on metal there. Maybe someone greased it up tracking down squeaks. I don't see how it could get that greasy otherwise.

Actually, I greased that one when chasing a squeak.
I eventually found the source elsewhere.

Darn it you guys - I fabricated my shims today, bought longer bolts and was all set to level that cab tomorrow; now you’ve got me wondering if I should drop both shackles and replace the bushings , a job I’m not especially excited about.

I believe there are bushings in the rusty shackle, but without the familiar shoulder. (See images) Again - I suspect that unit is an aftermarket piece; maybe it came with shoulder-less bushings.
One of the two bushings in the greasy, older looking shackle looks pretty good, the other does show age on the shoulder.

I have driven the truck extensively; there are no obvious symptoms of worn out bushings.

Rebuilding the shackles isn't a bad job. Your second set of photos don't show the bushings to be terrible, but the first ones looked like the bushings were worn radially, with the bolt not appearing centered in the eye of the shackle. You'll have to make the evaluation of how bad they are. I can see some cracking on the bushings on the rusty one, indicating that they may be going. The replacement bushings I got from Jim Carter do have shoulders on them. Link

You can always shim the cab level for now and refurbish the shackels when you have more time. You will need to remove the shims to rebuild the shackels so no big influence other than working on that area twice.

Tomorrow I’ll drop that driver’s side shackle to shim the cab.
That will give me a good opportunity inspect and assess the bushings. It would be a simple matter to loosen the other side for inspection also. I’ll decide on bushing replacement based on those findings.

As to the “when” factor, the truck is in a nice old repurposed factory building, clean , heated , well lit. The seats and fuel tank are removed. It’s now or never for those shackles.
It’s just that there are other projects I actually look forward to starting , and my fuel tank situation & now the question of cab mount bushings are pushing those fun jobs further down on the calendar.
It seems that one thing leads to another, and I’m sure that I’m the FIRST vintage truck owner to ever experience that syndrome!
Right?

I appreciate the input , complaints notwithstanding.

Save yourself a big headache before you rebuild your shackles.
1) place a piece of 1"X4" between the cab and the frame near where the shackles go. A 1"x4" is 3/4" thick. That will level the rear of the cab exactly like what brand new shackles would.

2) move to the front cab mounts and check for collapse cab mount supports. It they are not collapsed, shim the front cab mounts to specs.

This should give you a perfectly level can

3) put the rear shackles on and remove the 1"X4"s.

You shouldn't need to add much in the way of shims for the shackles if they are in good shape.

Carl -
Your recommended procedure suggests that there is a range of positioning available in fastening the rear cab mounts.

I am not aware of any adjustment other than shimming.
What am I missing?

Waveski , 52Carl mentions shimming and that is the only "adjustment" you have to obtain the correct distance from the top of the frame to the bottom of the cab.

Now for the bushings, strongly suggest you remove the shackles and replace the bushings.

While you are at it, check the front mounts and their condition because they can affect the cab "level" plus you need to loosen them while working on the rear mounts anyway. If you have the factory assembly manual look on Sect 1, sheet 3.09 for the front mount instructions .....distance from bottom of floor panel to frame is 1.83" +.060 , - 0 .

For the rear mounts (shackles) go to page 3.12 . The distance there is .760" +.060, - 0 .

Its not overly difficult to do, I did it on my 1954 3604. It makes a big difference on the "alignment" of the pedals to their respective openings in the floor panel as well as the steering column, etc.... note that "level" is a subjective term when thinking about the cab getting those distances within spec puts the cab where it's supposed to be in relation to the frame.

PM me if you wish to discuss and we can.

Once you've done the work, you'll be glad you did.

Copy, thank you.

Closing report–-
I believe that the difference between my cab & box was based on 2 factors:
- the damaged coil springs that were torched by a previous owner, one (drivers side) being lowered/ ruined more than the other
- the difference between the 2 rear cab mounts.

As shown earlier in this thread, the drivers side shackle assembly looked much newer and otherwise different from it’s partner. I have to conclude that the newer looking unit was not to spec. Measurements as per recommendations offered here supported that conclusion.

Coil spring replacement improved the leveling of the cab. Before the spring swap the difference was approximately 7/8” ; after swap 3/8”. Yesterday I dropped the drivers rear shackle and after loosening the other mounts I put in place three 1/8” shims and , ta-daaa - good results.

That differential has been annoying me for 2 years. Yesterday was a good day.

Thanks for holding my virtual hand and for the input. I learned a great deal from it.

Thanks for the feedback on fixing it.