Is This Angle Normal for a Drag Link End? Chasing Death Wobble

posulli

posulli

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Joined
Aug 22, 2020
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Location
Denver
My new to me LJR has death wobble (I drove it home from SLC to Denver when I bought it and had no signs of DW). Here is what I know:

_I did the dry steering test and discovered the adjustable track bar bushings were shot. The track bar was one of the few parts on the jeep that was not from a brand I consider up to my standards so I replaced it with a currie adjustable track bar.

_After replacing the track bar I was back on the road at highway speeds I hit a bump again and had death wobble again. Back to the dry steering test and further inspection I noticed some of the control arm bushings were also not in great shape. Ive always wanted Savvy's fully adjustable control arm set so I bit the bullet and replaced all the control arms. The old control arms were JKS but some were not adjustable. I wanted the ability to adjust so it made sense.

_As part of my build plans I wanted to do Black Magic's Vanco big brake kit. This thing is on 35's and had stock brakes. So at the same time I installed the control arms I also installed the big brake kit. I did new spicer ball joints and timken unit bearings at the same time because I was in there. Got it aligned and back on the road and it was doing great for about a month. Highway driving felt great and the jeep overall tighten up which was nice.

_Fast Forward to this weekend I had a 160 mile round trip up to Fort collins on Saturday and the jeep did great. Before leaving I checked the torque on all my control arm bolts, and track bar bolts, all were perfect. On Sunday I did the same trip and had a pretty bad incident of Death wobble on the way up to Fort Collins :mad:. I went the rest of the way to my destination and home on city streets to avoid DW again (man was that slow haha).

At this point the jeep has:
_New Currie Track Bar
_New Savvy Adjustable Control Arms
_New Big Brake Kit
_New Front Axle U Joints (Spicer)
_New Ball Joints (Spicer)
_New Unit Bearings (Timken)

All of this was planned except the adjustable control arms so I am not sweating it too much, but I am running out of ideas. The only thing I can think of is the axle housing bushings for upper control joints. I probably should install the currie Johnny joint kit so all the control arms are johnny joints.

The steering is a Currie Currectlync System and all tie rod ends and drag link ends feel good. The only thing I noticed today was the draglink end at the pitman arm was at a severe angle, is this normal?
IMG_3553.JPG


Any other thoughts?
 
Do you have a level pic of your pinion? Looks very low in the pic , but could just be the angle of the picture.
 
The joint between the Pitman arm and drag link is a ball joint so that angle is normal. It changes as the axle moves up and down.

In my experience the most common trigger of Death Wobble is an imperfectly balanced front tire. Not many tire shops allot enough time to the tech to get big tires perfectly balanced. I have needed to get my tires balanced 3X in one day before they finally got it right so I had no more DW.
 
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Ill have to get a pic tomorrow and measure. In the meantime these were my alignment specs. rear track bar is non adjustable and a tiny bit long which is why thrust angle is not perfect.
IMG_3558.JPG


Gollywomper said:
Do you have a level pic of your pinion? Looks very low in the pic , but could just be the angle of the picture.
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Jerry Bransford said:
The joint between the Pitman arm and drag link is a ball joint so that angle is normal. It changes as the axle moves up and down.

In my experience the most common trigger of Death Wobble is an imperfectly balanced front tire. Not many tire shops allot enough time to the tech to get big tires perfectly balanced. I have needed to get my tires balanced 3X in one day before they finally got it right so I had no more DW.
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The good news is I am getting new wheels and tires this Friday. The wheels and tires on there now are just not what I want. So I will make sure they are balance correctly. Im having a 4x4 shop do the mount and balance who has a very good rep. @Jerry Bransford you thing I should install the currie johnny joint housing kit so all my joints are johnny joints? https://www.rockjock4x4.com/CE-9102K-Jeep-XJ-TJ-LJ-MJ-Frontend-Housing-Johnny-Joint-Kit-7-16-Bolts
 
posulli said:
What would you suggest I be at?
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Toe-in should be .30 total or .15 per side. Factory caster angle is 7 degrees for stock size tires. The required caster angle reduces somewhat as the tire size increases. What size tires are you running?
 
If Jerry can’t respond he subs it out to me -

1/8 of toe in , 6-8 degrees of caster.
 
posulli said:
The good news is I am getting new wheels and tires this Friday. The wheels and tires on there now are just not what I want. So I will make sure they are balance correctly. Im having a 4x4 shop do the mount and balance who has a very good rep. @Jerry Bransford you thing I should install the currie johnny joint housing kit so all my joints are johnny joints? https://www.rockjock4x4.com/CE-9102K-Jeep-XJ-TJ-LJ-MJ-Frontend-Housing-Johnny-Joint-Kit-7-16-Bolts
Click to expand...
That would be a good long term decision.
 
Gollywomper said:
7 degrees may be a bit excessive on caster. Did you have the issue before and after the alignment?
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yea, I had death wobble before the alignment. But I don't know what my caster angle was before because I installed adjustable control arms before getting the alignment.
 
posulli said:
I am running 35's
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Between 5 and 6 degrees. It'll end up closer to 5 than 6. Even 5 degrees of caster angle can be hard achieve due to it also directly affecting the pinion angle. Trying for enough caster angle can create excessive pinion angle which causes vibrations.

The rule of thumb is to get as much caster angle as you can before it causes an excessive pinion angle thus vibrations.

Pinion angle is more critical than caster angle, you just want to achieve enough caster angle so steering is stable on the highway with good return to center.
 
Thank you all for your insight and help! One clarifying question that is pretty dumb haha. @Jerry Bransford when you say "Toe-in should be .30 total or .15 per side" my current front total toe on the print off reads .34 so it should be at and read .30? I could set this myself but sounds like I need to go back to the alignment shop and have them set up my caster correctly so could have them adjust that as well.
 
My apologies, I was looking at the initial alignment numbers not current. Your caster is now good and your toe-in is now just slightly excessive at .34.

That's what I get for trying to read the alignment data with my cellphone lol.
 
Ok well thats a relief! So maybe the tires not being balanced properly (new wheels and tires Friday so that should handle that). And upgrading the housing bushings to the currie johnny joint system. I can't think of anything else that would be causing death wobble with everything I have replaced...
 
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So I just did another dry steering test and the axle side of the Currie track bar has some movement. I rechecked torque right before the death wobble incident. It was at the75 ft pounds Currie specs. When I drilled out the holes to fit the bigger Currie hardware the holes looks good but maybe the the back hole was slightly oblong? Also looks like there is a little play in the upper control arm bushings that are on the axle. So replacing those with Johnny joints makes sense. What do I do about the track bar?
 
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posulli said:
So I just did another dry steering test and the axle side of the Currie track bar has some movement. I rechecked torque right before the death wobble incident. It was at the75 ft pounds Currie specs. When I drilled out the holes to fit the bigger Currie hardware the holes looks good but maybe the the back hole was slightly oblong? Also looks like there is a little play in the upper control arm bushings that are on the axle. So replacing those with Johnny joints makes sense. What do I do about the track bar?
Click to expand...
The clamping force of the bolt should be enough to overcome any slight Play in hole diameter.
 
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