Truck can't get aligned, pulls right

(anyone reading this thread now should just jump to the end - long story short, my alignment issues had nothing to do with the rear end)

Long story short, I've had a real bad pull on my truck for some time now because the rear thrust angle is pretty far off in the red. I'd have to dig out an old alignment sheet to get the exact numbers, but it is. Of course there are no alignment adjustments to be made in the rear, hence my concern.

For a long time I thought it was my leaf springs, maybe bent center pin or something to that effect. But I recently installed some custom built Alcan leaf springs and the issue persists even after install.

I also wondered if maybe my rear axle housing itself was somehow sitting askew, but I took measurements on both sides going from the housing to the front main eye bolt of the leaf springs, and the measurement is equal side to side. So that tells me (at least I think so) that the rear axle housing is straight and true.

What IS uneven side to side though are my tires. My rear tire is 1 inch closer to the back of the wheel well on the passenger side than it is on the driver side. So if the axle housing itself is straight, the leaf springs are good, but the tires aren't sitting in the same spot side to side, am I looking at a bent axle shaft?

Trying to get an idea from those wiser than me before I commit to a fix, thanks in advance

 

That's interesting, I'm following along for the fix. I have no idea. I would think an axle shaft that bent would cause some serious vibrations from the frequency at which it rotates. Either way, good luck.

 

I do have vibes, I probably should have mentioned that. Nothing super intense though, then again maybe I've just gotten used to it lol. I installed shims on the new leaf springs and it helped, but they're still there. Mostly at highway speeds. The pull is the big issue though, it's pretty strong even at normal speeds.

I ordered new u-bolts that should be here soon, there was an issue with the ones Alcan sent me so I had to temporarily reuse my old ones. When I go to install the new ubolts later this week or next, I'm going to look at this more closely while I'm under there with the rear axle dropped. I was hoping maybe it was something I botched on the leaf spring install that created the pull, but my axle housing to frame measurements being equal side to side tells me that's not the case. At least I don't think so

 

You've ruled out the leaf springs. But who says the spring hangers are true side to side?

 

Wouldn't that cause the entire rear axle to be askew though? As far as I can tell it's straight since the measurement from the center pin mounting hole to the front hangar is the same side to side

 

Also I guess maybe you should define 'pull'? If the rear axle isnt parallel with the front, then it will kind of crab down the road right? Not sure if I'd call that a pull or what

 

That was my question I was about to ask. If it's identical from front mounting bolt to the center pin, that'd mean your axle housing is nice and square. Something would be going on with your tire/bearing/axle itself. Very odd.

 

It's a strong pull, if I let go of the wheel it wants to pull strongly off to the side. I can let it follow a curve in the road by doing so. The front alignment is good, I've had that done a few times to rule it out and it's always the rear thrust angle that looks off on the printout.

 

I guess I could try jacking up the rear and spinning each wheel by hand to see if it one side looks wonky or not. Haven't tried that yet.

 

What if both sides were bent at the differential in the same direction. Your measurements would be good. Just a thought

 

I'm still suspicious of the axle housing. A bent shaft would give you a vibration, but i would be amazed if it could move your tire back an inch.

I wonder if you could use a plumb Bob and some chalk on a level surface to lay down a diagram. Maybe take a point front and rear of each tire, and at each end of each axle tube, and at various points along the frame. Then move the truck , get out a square and look it over.

 

yeah I can't completely rule out the axle housing with tape measure measurements, that is true. That's a good idea on how to check, I'll give it some thought. If only my driveway weren't so old and uneven lol. I'll have to find a good place to give that a shot.

 

Thats all good and fine, but what if the front bolt is not symmetrical from side to side? What if the frame or front hanger is tweaked somewhere?

Measurements are only as good as the reference

From what Ive seen around here I seem to get the impression @eon_blue wheels kind of hard

 

I used to but it's been over a year since I've done any hard trails. Wife and I had a baby not that long ago and it slowed the hobby down some for the time being. But I can't rule out that it may have happened on a prior trip.

If the frame got jacked or bent that would really surprise me though, I've never gone that hard on any trail lol. 4lo and slow for me

 

Maybe park it on a piece of plywood?


Or maybe some sort of contraption involving lasers and magnets.

 

That second option reads like math to me, but I am thinking there's gotta be an easy way to test the axle housing. When I put the new u-bolts on I'll do more measurements on the axle relative to the frame on both sides to try and verify.

 

Sounds like the axle housing is off center side to side .

Which would still give you the same distance from center pin to spring hanger

You said one side is a inch closer is the other an inch further away??

 

The tires are, yes. Driver side tire is about an inch closer to the cab than the passenger tire is. Which would account for the strong pull.

The more I think about it, the less likely it seems like a bent axle shaft would create the same constant pull all the time. I think you guys are right about it most likely being the housing, I will still try and verify but then the question becomes how and what to do. I could take the leafs off again and re-install, making sure the axle is straight before torquing it all down. Unless the reason it's askew is due to the frame, which I doubt

 

True, just trying to see what possible explanations might be. I might just have the 4x4 shop down the street that does my alignments take a closer look at it and tell me what they see.

When I do the u-bolts in a few days I'll have the axle loosened from the springs, I can see if maybe it's as simple as lining it up and retorquing it all back down. But since there's no leeway in the center pin mounting holes, I dunno if that will end up being the case.