Rear axle "alignment" and rear tire wear

[pmou]

OK so, got something weird going on with the rear end.. gonna try to explain as best as possible (and please be patient with my ignorance, I have not owned a solid axle vehicle before):

currently, i have the JOR kit installed with new shackles and hangers. I verified today that they are all in the correct orientation.. I will take pics (see next post) for sanity but for this moment let's assume I am not a total space cadet. Also did leaf spring bushings at that time and new shocks. Left the stock leaf springs (hence bushings). This van was in a front PS accident that required a new front body panel and new PS door. Nothing past that that i could see in the immediate area when i bought it. There's definitely something minor in the front rad support & bumper is slightly tweaked (the actual bumper, not mounts, crumple zones, etc). Subframe looked untouched as well as all suspension parts so i thought good.

The van had some real old tires on it, fine with me i was going to put bigger ones anyway. I noticed right away that the rear DS rear tire had heavy camber wear on the outside knobs. figured the van had just never been aligned at all. Installed lift & 30.5x10.5 tires on new rims. When i went to install the shocks, i noticed that the mounts seemed to be off to the PS. Enough so that the DS one would have rubbed the mount if I didn't space it out to the PS at the top mount about 3/4".. which I did just to have the thing be driveable. Thought maybe it had just been sitting and a quick drive around the block everything settles in and we are good. Well, it's still off. The tires are also noticeably sitting in different spots relative to the wheel wells, off to the PS. I did about 900 mi of driving on it over the weekend, was planning to get an alignment after that. Even just in that short amount of time the outside knobs on that driver side tire are wayy worn, like noticeably so and have lost some minor details that no other tire or part of a tire is showing.

Called firestone as that's where I'd usually get an alignment. They said there's no adjustments to be made there, and they will need to do a full inspection before the alignment to figure out what is bent or otherwise off.

Called a shop I usually use for diff and transmission work, they said this wouldn't be anything internal to the axle which is about where they stop. He suggested bent leafs.

Anyone else want to throw something out there? It'll be going to firestone on monday as that's the soonest i could get it over there, but I'd like to have a little better understanding as to what is going on before I hand it off to them.

[pmou]

Also just want to mention that the "camber wear" was _definitely_ there before the lift, tires, wheels. Off center, I am unsure but it would seem to make sense in my head that it was as well.

[dcsleeper]

My only guess is that you swapped one side's leaf spring end to end.

The springs are not centered on the axle, they have a long and a short side. I don't remember which should be where, but you can still go look.

[pmou]

My only guess is that you swapped one side's leaf spring end to end.

The springs are not centered on the axle, they have a long and a short side. I don't remember which should be where, but you can still go look.

This is possible, however it would not have been me as I didn't remove the leafs from the axle (nor loosen them, or anything of that nature). They are sitting relatively centered fore-aft in the wheel wells with the shackles so I am hesitant to think that is it. Is there any obvious identifying features other than length that would indicate orientation?

[pmou]

Here's a couple of shots from a little ways away of the rear:

edit: street is not level, frontend of car is downhill... it's slightly more level in real life

[MiniAlt]

how about jacking up the rear on the body so the drivetrain is free and giving everything a good hands on shake and see if anything’s loose. worn wheel bearings?

[pmou]

how about jacking up the rear on the body so the drivetrain is free and giving everything a good hands on shake and see if anything’s loose. worn wheel bearings?

So, i just did that as you suggested (i believe) -- both wheels can move laterally (axle in/ out of housing) slightly when in the air. I did one wheel at a time, and they both would turn both directions with some resistance, no grinding or noise. I figured the resistance is the mechanical disadvantage on the driveshaft / neutral gear?

When attempting to push / wiggle fore/aft (relative to the vehicle ie fore = towards driver seat) i got nothing, no movement. felt rock solid.

Vertical, i got a slight clunk on both wheels. A little hard to be certain it wasn't the lateral movement/ clunk i described in the first step there. I did my best to put all my weight into the top of the wheel during this, and then lifted the bottom of the wheel using my knee (so as to avoid pulling the wheel in/out) and i got a small clunk / movement.

Could this be bad wheel bearings? and if so, wouldn't that mean the wheels would be more likely to "sag" ie inside edge wear?

[pmou]

took the wheels off to look around and play with the axle. didn't really see anything glaring. I thought the leaf spring "center pins" might be bent, but I checked my housemates astro and his also appear to be not centered in the hole in the clamshell.

tool a couple pics of the lateral slop I described. I'm assuming this is not an issue? it's gotta be less than 1-2mm

in

out

[pmou]

here's the center pins

driver side

passenger

[SportsBoy]

That DS leaf does look weird.... If you have new hangers and shackles, it seems like the leafs and clamshells are the most likely thing that is wrong imo

Unless the whole axle assembly is bent or something, but that seems unlikely as all get out.

[pmou]

yeah.. that's what it's coming down to in my head. I'm comparing wheels to wheel well, and it doesn't change by rotation so that rules out hub/wheel/inner axle. shackles and hanger are brand new (and didn't get dinged). could be off, but the tire wear was present before the new parts. that leaves leaf springs (or possibly sleeves/bushings.. but those are new as well.. and should just center under the weight I'd think), where the leaf springs attach to the axle, or the axle housing. the shock mounts being off tells me that it's likely that the axle is ok, and whatever is positioning the axle relative to the body is the problem? which would put us at the mount that is welded onto the axle/clamshell/leaf springs...

[pmou]

however, would that explain the tire wear? is there some way that the leafs could be bent that would explain the weird pressure on the outside of the tire?

edit: I suppose this could be explained by "dog leg" ie the rear is not square to the front so when I'm driving straight I'm actually driving like 2deg to one side or another, and this is what is causing that weird wear.. not actual camber

[pmou]

ok also found this interesting:

https://www.knowyourparts.com/technical ... tire-wear/

they mention the thrust and setback angles.. which is more or less what I was describing. if the back isn't square to the front, it essentially is driving force against the front wheels and will cause excessive wear on the back tires, almost like toe in or out. My guess is that's what is going on. anyhow, I think this will all be more clear once firestone shoots a bunch of lasers at my car to measure stuff, I think that may be the best way to figure out what the hell is off.

edit: another good one - http://prod.lv2014.gener8cms.net/index. ... k-tracking

[Mmusicman]

Note sure if this should be considered relevant.. since my rear issues were lift related.
My problem however did not cause unusual tire wear either.

I found my axle/springs were moving within the clamshell.
(it finally explained why I kept seeing different driveshaft-yoke engagement measurements)
They weren't always moved evenly or the same distance either.

I finally resolved "my" rear-end shifting by not only clamping the clamshells tighter (which distorts them if using lift blocks)... but I also added a wide-centering pin (not sure what to call it) to prevent the rear from being able to move withing the clamshell. I used literally a "socket" that fit the opening. It worked perfectly for me... no more movement.



Recently (while doing pinion shims with axle loose) I did some numerous and careful measurements (to various different frame points) to ensure the rear was tracking square. I found it still off a little and (in my case) attributed it to axle positioning under tall lift blocks. In my case.. I applied a little "DIY rear axle alignment".. pulling on the rear before positioning lift block and tightening it all up. Seems to have worked for me as well...



Understand that most of my issues were due to lift modifications and the vehicle no longer being stock.
Here's my post about the pinion shims...
https://www.astrosafari.com/viewtopic.p ... s#p1563390

[AstroWill]

I found my axle/springs were moving within the clamshell.

Seems somewhat common, u-bolts and plates are a nice upgrade IMO.

[MechBob]

Before getting carried away,take it to a good quality 4 wheel alignment shop.When an alignment is done,you can usually accomplish an acceptable "thrust" measurement,because the machine accounts for this while adjusting the front end,and if still out,most will try to shift the rear,as music has done.This is why we see very little "dog tracking" like the old 2 wheel alignment days.Also,if your suspension is "wacky" in a vertical plane,there will be no unusual tire wear from alignment,just the body would be "wacky".These small rear diffs are known for bending the axle tubes,up,down and front to rear,if smaller,an good alignment can make tire wear acceptable.Also,I have,over the years,seen what people assume is camber wear is actually from high speed long sweeping turns.Guilty of that myself.

[pmou]

Wow thanks for the detailed input mmusicman and mechbob. After seeing what you did there music, I'm thinking it may make sense (as bob said) to take this to a 4wd shop that won't just immediately blame the non stock parts (idk if firestone would do this, but it would make sense to me). I'm impressed by your resourcefulness music, but given how badly this is wearing the tires (and rubbing) i think i'd prefer to just hand it off to the pros and get it all looking good. I'm going to check today and see if there's a 4wd place in town that could take a look at it.

[pmou]

OK, i talked to Spruce 4x4 in boulder. they said i can stop in and take a look at it on the lift once they have measurements. Their opinion was if the back is off, it means that the center pins on the leaf(s) are bent, the axle is bent, or the body is bent (hopefully not that). They said if it's the body they would send me to a body shop to put it on a frame rack. It'll be there on wednesday.. see what we find out then.

[Mmusicman]

In my case... nothing was bent.
The springs were just sliding back and forth inside the clamshell.

None the less.. good to have a pro look at it.

[pmou]

yeah, the fact that it has been in an accident has me concerned.. and the fact that the tire wear happened in a really short amount of time. I think in this case I'll take the peace of mind for $100. also seems like a cool shop so I can see what they think and likely have them give it a look over.