XJ wandering - everything seems correct.

[blistovmhz]

What you have is a y- link or radius arm. That disproves my theory if housing rotation so now I'm not sure. Is your camber the same at both knuckles?

Camber is the same on both ends. As I've said, the alignment looks perfect. Like, normally I'm not terribly anal about alignment numbers on a truck this big, with wheels this big, as my experience has been that the bigger I go, the less precise I need to be with alignment.
This truck however, has had this issue with pulling left/right for quite a while, and it seems the bigger tires I install, the worse the problem gets, which keeps bringing me back to thrust angle and/or lockers and/or gears.
Deeper gears would definitely amplify a tire size discrepancy, but the problem happens with 3 sets of tires. I'm sure all three sets didn't have the same discrepancy. That pretty much, in my mind, leaves me with thrust angle. If there was any thrust angle outside 0 degrees, bigger tires, with lockers would definitely amplify the problem. But of course, I can't find any problem with the thrust angle when it's parked.
I'll try to rig up a camera under the Jeep this afternoon to see if something is moving.

 

[SolarBell]

If you have a lunchbox locker, I say to remove the rear locker and put back in the spider gears and then see if the problem goes away.

 

[blistovmhz]

Sooo much work though!!
I may try that later, as it really only proves if the problem is related to differential lock, and nothing about torque in general. It'll be my last resort I think. Will try swapping left/right tires tonight, as well as try to get some video of the suspension.

 

[blistovmhz]

Sooo much work though!!
I may try that later, as it really only proves if the problem is related to differential lock, and nothing about torque in general. It'll be my last resort I think. Will try swapping left/right tires tonight, as well as try to get some video of the suspension.

Oh, actually, I can rule out the rear axle thrust angle, and tire size all at once simply by removing the rear drive shaft and driving in front wheel drive! Huzah!
I'll try this as well tonight, before swapping tires and hooking up camera. This should completely confirm if the issue is being caused by leaf springs, rear locker, or anything on the rear axle.

 

[eflores]

Do any of you guys experience bump steer?

 

[blistovmhz]

Do any of you guys experience bump steer?

Yes, but not due to bad drag link/track bar angles. Just the nature of the crossover steering. I guess it's not really "bump steer" officially, but I'm not sure there's a term for it.
As mentioned above, with Crossover, especially if your steering is relatively flat to begin with, as the front end comes up, either the wheels have to pull left, or the steering wheel has to turn right.
Had I really considered this before building my steering, I'd have just gone with a beefier inverted Y, as it keeps your drag link angle up, gives you a longer draglink, and half of the "up travel" of the drag link is divided into the tie rod, which results in toe in.

 

[blistovmhz]

Got a video from under the Jeep, front and rear. Uploading now. I didn't see anything obviously wrong. All the joints/bushings seem tight and nothing seems to be shifting.
Leafs look like they may be wrapping a little more than normal, but I suppose I've never really watched a leaf from this perspective. Will be uploaded in 20 or so minutes.

 

[ColoradoRaptor]

Something is moving/shifting causing this problem during acceleration and deceleration. You may have many new parts but my guess is you forgot to tighten something or something is worn out. The camera idea is good if you have it underneath and are recording what happens as you drive. Check your U bolts and leaf bushings really good!

 

[blistovmhz]

https://www.youtube.com/watch?v=Wn7zfUEPb2I

Here it is. I can't see anything wrong unless someone thinks my leafs are wrapping too much.

Sorry, took a minute at the beginning to get going. Had to herd cats back into the house. Video also switches to watch the front end half way through.

 

[unhitched]

is that a rough country long arm kit? if so are the bushings going south?

 

[blistovmhz]

Yes rc. Bushings all seem fine. Recently serviced the joints on both arms, but they were pretty snug already. Bushings seem brand new.

 

[TanasiXJ]

Caster. Caster. Caster.

My similar setup was doing the same exact thing. Went from 4° caster to 5.5°. Problem solved.

No more wander, drift and pulling................

 

[blistovmhz]

Caster. Caster. Caster.

My similar setup was doing the same exact thing. Went from 4° caster to 5.5°. Problem solved.

No more wander, drift and pulling................

Was going to give caster a try again. It's definitely set where it should be for any of my other Jeeps, but perhaps it's dramatically more sensitive with the bigger shoes. I'm definitely within' at least 75% of a degree, but maybe that's just not enough with 35's.

 

[old_man]

XJ's don't wander....they just pick their own line.

 

[ColoradoRaptor]

XJ's don't wander....they just pick their own line.

:yelclap:........... :roflmao:

 

[blistovmhz]

XJ's don't wander....they just pick their own line.

heh. This is the first of my 6 XJ's that I couldn't get tracking straight.
I THINK I tracked down the issue though.
The upper control arms were fighting each other, and turns out those wee d30's do twist a lot.

When I first tried to get this resolved, I thought the issue was caster, so I backed it off a little, then it just got worse. Then I discovered the lower right arm was somehow 1/2" longer than the left, so I verified the thrust angle of the rear axle, and lined up the front with the rear. The symptoms changed slightly, but still pulling on accel and decel. Turns out when I adjusted the caster the first time, I must have had one side of the Jeep flexed out a bit, because when I tipped the axle back far enough to pull out one of the left upper arm bolts, the right side was still crazy tight. Had to give the jack two more pumps to get the axle rotated back enough to pull the bolt. Derp.

So took for a test drive, pull is almost completely gone. Now it's just feeling like a little too much caster, so I'll back it off tomorrow and see what she does. Either way, 60 is no longer scary, so PROGRESS MADE!

Also, I should've known better because I lectured a bunch of guys on this exact issue years ago, when they were complaining that their RC upper arm bushings were failing in a few months. RC's uppers are different lengths, but they don't mention this in the instructions, so when most guys go to install them, they get one installed and realize the other one is 1/3" to a 1/2" too long or short, so they just twist the axle until it fits, thus putting constant strain on those poor bushings. Again, *derp*