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Discussion Starter #1 (Edited)
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.

 

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Discussion Starter #2 (Edited)
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.

 

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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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Discussion Starter #4
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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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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Discussion Starter #6
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. :shaking:
 

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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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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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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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Discussion Starter #10 (Edited)
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. :mad3:
 

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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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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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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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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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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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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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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 :flipoff2:
 

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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.
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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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
 
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