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Old 08-12-2019, 04:39 PM   #1 (permalink)
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Question Rate my steering angles - why is it bump steering?

Built this long arm and D44 swap front suspension a few years ago for my wife's Cherokee. Drove it instead of trailered it for the first time in a long time and it was a bear to control down the highway. I thought I got my angles and lengths "close enough" but what are your thoughts?

The track bar is 36.75" long and is currently on the bottom hole of the frame-side track bar mount, sitting at 2.0* from horizontal.

The drag link is 37.50" long and is sitting at 2.5* from horizontal.

The tie rod from knuckle to knuckle is perfectly horizontal and independent of the drag link, and 57.25" long.

Castor measured at positive 7.4* on both knuckles.

Symptoms: Bump steers mostly to the left on highway bumps, and experienced 1 episode of death wobble when hitting a bridge expansion joint.


Last edited by OldMan57; 08-22-2019 at 12:07 PM.
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Old 08-12-2019, 04:56 PM   #2 (permalink)
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In case anyone's interested in the 4 link calc's, here's what putting in the exact measurements of how it sits today into Triaged's calculator.

I'm pretty sure I still need to move the frame side upper link higher so that it's parallel with the axle side link.


Last edited by OldMan57; 08-22-2019 at 12:08 PM.
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Old 08-12-2019, 05:08 PM   #3 (permalink)
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Move the PH up a hole and dump the poly?

PH adjustment is free. Drive it around the block.

It looks like you have BF poly joints, nothing wrong with those except the application. The trac bar LATERALLY LOCATES the axle. It darts because the poly gives under the extreme load of the vehicle and the steering forces.
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Old 08-12-2019, 05:14 PM   #4 (permalink)
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Move the PH up a hole and dump the poly?

PH adjustment is free. Drive it around the block.

It looks like you have BF poly joints, nothing wrong with those except the application. The trac bar LATERALLY LOCATES the axle. It darts because the poly gives under the extreme load of the vehicle and the steering forces.
On the track bar/panhard bar as you call it - the one end is a heim and the other end is the BF poly joint. Curious, what would you replace the frame side with?
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Old 08-12-2019, 06:07 PM   #5 (permalink)
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Simply another heim/rod end equivalent that fits your mounting width.

Have you tried or measured the trac bar angle before in one hole higher? Dunno if you’d overshoot the angle and defeat the purpose of my suggestion to gain that angle to match the drag link
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Old 08-13-2019, 01:19 PM   #6 (permalink)
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From my experience working on Jeeps, it seems like most of them have rubber bushings at each end of their track bar, or rubber on 1 end and tie rod on the other. Wouldn't this be worse than a poly/heim combo setup like is on my wife's Jeep?

Moving the track bar frame side bushing up 1 hole made for 3*. As seen in the first picture I posted, the lowest hanging hole nets an angle of 2*, and the next hole up is 3*. The drag link is 2.5*...so I'm either above it or below it by 0.5* degree.
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Old 08-13-2019, 09:44 PM   #7 (permalink)
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Poly may be more dense than OE rubber but it still gives. Any amount of deflection is unwanted. As I mentioned in bold (wasn’t keyboard screaming, just emphasizing) you want the axle constrained in the lateral plane without any variables or deflection and there’s no need to isolate the chassis from the axle with a poly joint. There aren’t any consequences to dumping the poly on the trac bar, only benefits.

Most OE trac bars are one-piece non adjustable so from a production and service standpoint rubber bushings are found in that application but much smaller than your large joint.

10-4 about the adjustment hole/angle dilemma. Kinda figured after I thought about it. .5* probably isn’t that big of a deal.
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Old 08-14-2019, 09:04 AM   #8 (permalink)
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Pics aren't working for me.

The poly isn't causing your problems. OEMs have been using rubber at both ends for decades. I've been running poly at my frame and a heim at the axle for 10 years on a D44 that sees thousands of road miles per year on 37's. I run my setup until the panhard heim gets sloppy and I still don't have any instances of death wobble. Coil sprung radius arm setup for what that's worth.

Are all of your steering joints tight? TREs, DLEs, BJs, etc? How old is the steering gear?

Check out this link if you want some casual reading. They address the causes of death wobble about 3/4 of the way down the page.

Link to AGCO steering page
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Old 08-14-2019, 09:52 AM   #9 (permalink)
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How are your ball joints? How are your control arm bushings? Are all your bolts, jam nuts, steering joints tight?

From what I've seen its usually one main issue and everything else is just a little meh and the combination of things makes it really bad.
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Old 08-21-2019, 08:36 PM   #10 (permalink)
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Are the pics working now? I still see them when I access from my tablet, my laptop using Chrome, and laptop using internet explorer.

The front suspension was built with all new Moog ends and balljoints in 2015, then the Jeep sat for 3 years. We just pulled it out of storage a week or 2 ago and drove it 8 hours on the highway and experienced death wobble and nasty bump steer at quite a few bridge expansion joints. It made for a long and tiring drive. The tie rod from knuckle to knuckle uses heims, and the drag link uses typical 1 ton TRE's at the pitman arm and high steer arm.

What about the Jeep's OEM steering box? It is leaking at the input shaft, and I'd imagine after 176k miles before changing everything under the suspension but leaving the steering box, it probably has some slop in it. This Jeep has no steering dampener, but I have a 1.5" DOM clamp from Ballistic fab I could make a mount from and bolt on a steering dampener/stabilizer... but I was hoping to eventually run hydro assist on this Jeep for when we're in the rocks, and to somewhat use the assist-ram as a stabilizer as well. Thoughts?

I can change out the poly bushing on the track bar with another heim and report back. Currently have the entire HVAC box out of the Jeep and dash town apart getting a rats nest out of the blower motor.

Last edited by OldMan57; 08-21-2019 at 08:37 PM.
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Old 08-21-2019, 08:48 PM   #11 (permalink)
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pictures are not working for me, laptop using firefox

if you are concerned about steering box, absolutely check it out and tighten it up if it is needed. if it wasn't having issues before, it shouldn't now but it is easy to jack it up and see.

a dampener isn't going to fix death wobble though it might help mask it a bit and won't do a thing for bump steer. bump steer is a drag link vs panhard angle/length mismatch typically. death wobble is a lack of control.
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Old 08-22-2019, 12:08 PM   #12 (permalink)
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Re-hosted the pictures elsewhere and edited.

Pics working now?
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Old 08-22-2019, 01:22 PM   #13 (permalink)
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I can see the pics now.

I’d check steering box myself. I’m stumped on the bump steer. My angles and lengths are way further off between the two compared to you. And there’s a little bump steer but not enough I’ll change a thing.
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Old 08-22-2019, 02:03 PM   #14 (permalink)
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a dampener isn't going to fix death wobble though it might help mask it a bit and won't do a thing for bump steer.
It might help the death wobble. It's a result of some sort of harmonic frequency oscillation and by providing damping it could either slow the frequency enough it doesn't continue. If it's just a shimmy that is, like baby death wobble vibes. Full on tire flopping it won't to squat.

I'd check all of your bushings in the controls arms as well.

Don't know what to say on the bump steer.
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Old 08-22-2019, 02:09 PM   #15 (permalink)
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Is anyone else bothered by the fact that the link calculations are for a triangulated 4-link with NO panhard bar, but OP's truck now has a panhard bar installed? That's a significant issue right there IMO and can definitely cause bump steer as the links bind up.

As for death wobble, something is probably loose in the front end giving you play in the steering.
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Old 08-22-2019, 03:36 PM   #16 (permalink)
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If your links are adjustable, reducing the castor a bit will rotate the steering arm down and bring the drag link closer to parallel with the panhard bar if it's mounted in that next hole.
Might be able to get enough to get rid of the +/- 0.5° dilemna...

This may even fix the death wobble - ~7° of castor is going to be trying to self-centre pretty aggressively and could be setting up your harmonic shake...
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Old 08-22-2019, 04:00 PM   #17 (permalink)
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How much triangulation does it have? I also bet the bump steer is from the 4 links. If there's near 40° of triangulation, it's not a maybe, it's definitely going to be the cause of bump steer.
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Old 08-22-2019, 10:56 PM   #18 (permalink)
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If your links are adjustable, reducing the castor a bit will rotate the steering arm down and bring the drag link closer to parallel with the panhard bar if it's mounted in that next hole.
Might be able to get enough to get rid of the +/- 0.5° dilemna...

This may even fix the death wobble - ~7° of castor is going to be trying to self-centre pretty aggressively and could be setting up your harmonic shake...
this just might be the first time i've heard somebody say 7* was aggressive
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Old 08-22-2019, 11:12 PM   #19 (permalink)
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Is anyone else bothered by the fact that the link calculations are for a triangulated 4-link with NO panhard bar, but OP's truck now has a panhard bar installed? That's a significant issue right there IMO and can definitely cause bump steer as the links bind up.

As for death wobble, something is probably loose in the front end giving you play in the steering.
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How much triangulation does it have? I also bet the bump steer is from the 4 links. If there's near 40° of triangulation, it's not a maybe, it's definitely going to be the cause of bump steer.
I’d pull an upper link on one side see if it goes away. It may handle like shit but shouldn’t have bump steer.
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Old 08-22-2019, 11:30 PM   #20 (permalink)
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check the unibody frame (both sides)around the track bar and steering box for cracks

and you should also switch out those tie rod ends on your drag link for some actual high misalignment drag link ends, wouldnt be surprised if theyre binding at full droop

Last edited by rockyota83; 08-22-2019 at 11:35 PM.
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Old 08-23-2019, 08:05 AM   #21 (permalink)
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I’d pull an upper link on one side see if it goes away. It may handle like shit but shouldn’t have bump steer.
That's what I'm gonna try shortly. I was reading a few things awhile back and mentioned the stock 4-link plus panhard on the front will bind causing issues but works in the factory range of travel. I know there isn't much flex in the new arms compared to the factory stamped units.
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Old 08-23-2019, 02:44 PM   #22 (permalink)
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Is anyone else bothered by the fact that the link calculations are for a triangulated 4-link with NO panhard bar, but OP's truck now has a panhard bar installed? That's a significant issue right there IMO and can definitely cause bump steer as the links bind up.

As for death wobble, something is probably loose in the front end giving you play in the steering.
I wasn't sure how to do a panhard/track bar with the 4 link calculator, so the screen shot from the calculator above is what the Jeep's 4 links are set to currently, plus a track bar.

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Originally Posted by wendleburger View Post
If your links are adjustable, reducing the castor a bit will rotate the steering arm down and bring the drag link closer to parallel with the panhard bar if it's mounted in that next hole.
Might be able to get enough to get rid of the +/- 0.5° dilemna...

This may even fix the death wobble - ~7° of castor is going to be trying to self-centre pretty aggressively and could be setting up your harmonic shake...
Interesting comment. I was under the impression that more positive castor would aid in highway stability, so the castor is set to 7.4 degrees on both sides. Factory service manual on the XJ states 7 degrees is the target, but that's for OEM suspension and a D30.


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How much triangulation does it have? I also bet the bump steer is from the 4 links. If there's near 40° of triangulation, it's not a maybe, it's definitely going to be the cause of bump steer.
I don't believe the 4 links have enough triangulation by themselves to control the front axle, which is why there's a track bar in the suspension.

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Originally Posted by rockyota83 View Post
check the unibody frame (both sides)around the track bar and steering box for cracks

and you should also switch out those tie rod ends on your drag link for some actual high misalignment drag link ends, wouldnt be surprised if theyre binding at full droop
The unibody has been beefed up with frame stiffeners bumper to bumper. The aftermarket track bar frame side bracket was welded to the stiffeners. When we built the front bumper we also replaced the OEM aluminum steering box spacer with a steel version from Iron Rock Offroad, and used their bumper brackets/unibody tie in brackets to start building the bumper, so the steering box ain't going anywhere. It is, however, probably worn out and needs rebuilding.

The tie rod ends are of the 1 ton variety, but you're right in that they're not the ES2027 and ES2026 high angle parts. I'm fairly certain that the shocks would be the limiting factor on the front end before the TRE's bind, but this is good advice and I'll keep this in mind next time we get the Jeep flexed out.


To aid in the "bad weather/daily driver/wife friendly-ness" of this Jeep's purpose, I started looking at components of the suspension that might be too soft or nonexistent. We removed both sway bars front and rear when this rig was built, as back then it was intended to be a trailered vehicle. Now that it's serving dual purpose and might see some long stretches of highway before getting into 4wd, I wanted to address the shocks and sway bar aspect.

Currently the shocks are set up to be fairly flexible and soft.
  • Front shocks: Bilstein 5125 12" travel in a 255/70 valving
  • Rear shocks: 9.xx travel Bilstein 5100's in an unknown valving, meant for XJ with 4" of lift...forums are claiming 170/60 or similar valving

In the spare parts pile in the garage I have an extra pair of Bilstein 7100's in a 360/80 valving that are 12" of travel, and I'm contemplating rebuilding those and putting them in the front of the Jeep to stiffen up the jounce and rebound. Thoughts on this?

If I put the 7100's up front, I could move the 5125's that were in the front to the rear, effectively allowing 12" of shock travel fore and aft, and providing stiffer valving in the rear as well.

With about 1000lbs in the Jeep, the suspension would float up and down over a bump on the highway for a few oscillations and each up and down movement would jerk the tires as the suspension floated. To me, this indicates too soft of something.

I also picked up a 31mm WJ sway bar from the junkyard that I will graft onto the front to help reduce body roll. I did this on another XJ a few years ago that was meant for the street and it handled noticeably better over the XJ sway bar... can't imagine what it'll feel like over NO sway bar.

Thanks everyone for the continued support. I'll check back soon. Any other recommendations on what to look for?
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Old 08-23-2019, 02:49 PM   #23 (permalink)
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By the way, for anyone wondering, this is a 1998 XJ 4 door with a 4.7L stroker, AW4, 231 + SYE, F250 Dana 44 and GM 9.5" 14b semi float. Front axle is trussed with 4.10's and a Spartan. Rear axle is 4.10's and factory open diff for now.

This is the wife's wheeling rig.
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Old 08-23-2019, 03:29 PM   #24 (permalink)
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Interesting comment. I was under the impression that more positive castor would aid in highway stability, so the castor is set to 7.4 degrees on both sides. Factory service manual on the XJ states 7 degrees is the target, but that's for OEM suspension and a D30.
Assuming you have bigger tyres and less backspacing in the wheels than factory spec'd - that's giving whatever castor angle exists more leverage to work with, it's probably fighting itself pretty aggressively to stay straight.

We have major issues with this is Australia with the late model Nissan Patrol axles, which have an inherent geometry issue from new and will wobble and castor slap any chance they get if everything isn't perfect.

Subtle castor angle, slight toe-out and no play in the panhard bushings is the first port of call and seems to fix most of them.
Might work in your application, the forces are the same even though the steering wheel is on the wrong side and the water spins the wrong way down the drain.
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Old 08-24-2019, 08:45 PM   #25 (permalink)
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Have you tried seeing how the steering oscillates while at rest? Key the ignition … the jump up/down on the bumper (if you're heavy enough, or ask your mother in law to do it for you). See how much the steering wheel jerks back/forth. Alternately .. you could lay on the ground and push up with your legs … but would need to rely on your wife to tell you how much the wheel is moving back/forth. Maybe do the bumper first, so you can see the movement … and then get on the ground so you can see WHAT is causing the movement. Your legs will get tired eventually, FYI.


To me … those steering looks decent. Not perfect --- but definitely runnable. We've all see worse going down the road.


The DW (as opposed to the bump steer effect) leads me to think you have a failing part somewhere you haven't found or accounted for yet. Worn this, loose that, rounded hole somewhere, etc.

The 4 link angles are a bit more that what you would want since you are retaining the track bar. I'd probably keep that as a last resort … perhaps disconnect one upper and jounce the suspension again (after your legs recuperate)
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