OP
Death Wobble Question
- Thread starter taylormade73
- Start date
OP
Well, that was a half a step backwards. It also looks like the shim is distorting the race. Taking the arms back out and removing the shims from the frame side joints.
on a freshly greased JJ, it should move relatively freely. After a week or two you might need a wrench to turn the arms.
OP
All my JJs do move freely when I regrease and rebuild them. However, the upper fronts I have .04" shims on either side to increase the preload in a test on the DW I'm trying to diagnose. With the shims they have so much preload that they are difficult to move. I am removing the shims from the frame side upper joints as it took me a step back from the success I had shimming the axle side JJs. With only the axle side JJs shimmed, there was no DW, only a brief shimmy when hitting a specific bump that always triggered the DW.
JKLNHYD
TJ Enthusiast
I always trusted that some of the fine detail factors related to DW included the castor of the axle after the Jeep is lifted. If all your joints are tight, maybe try uniformly shortening your upper control arms to get the caster closer to a stock value? I'm no expert, however, you may have already tried this.
B00mb00m
The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
Just read through your thread, man, sorry you're having to deal with this and much respect for all the time invested. Consider this the tuition for you learning absolutely everything about your front suspension and you can hire your DW services out after this.
Sometimes in instance of extreme troubleshooting you have to go try a couple hail mary passes. So it seems the UCA's may not be fully capable of controlling the axle when a resonance (DW) begins. It could be that the UCA's are neither the source nor the result of the problem but just an intermediate in this whole issue.
Regarding the source:
It could be that the increase in mass of the new axle makes DW a problem where it wasn't previously. Is there absolutely anyone around that you could swap rims/tires with just to check if the tires are your source? IE your source could always have been there but just wasn't enough to set off a resonance.
Regarding the result:
Assuming you have a source that initiates the resonance, for whatever reason it seems to have fallen upon your uppers to do the work of damping it out. It could be the uppers are doing all they can but your frame rails themselves are not stiff enough. I believe I have seen where a trackbar brace or other between rail brace was added to stiffen up the frame as a box. @mrblaine you have added a support before to fix DW right?
Hail Mary:
I also had a bout with DW. When i did my JK axle swap i always had a shimmy of sort on certain one-wheel pothole inputs. It was there from the start when everything was brand new. It got worse when i went to 37's. My balljoints passed all the tests but when I pulled the knuckles they rattled back and forth easily but still didnt have up/down slop. I swapped out the BJs and hit the same pothole, no shimmy / DW. For reference, these were Spicer Balljoints which basically couldn't do the work even from the get go. Also note, i had bumpsteer so I was asking a lot.
Penance:
If all else fails, you can do what I did... cut it all off and go to Savvy Midarm. It's not like you'll regret going to a midarm either.
Sometimes in instance of extreme troubleshooting you have to go try a couple hail mary passes. So it seems the UCA's may not be fully capable of controlling the axle when a resonance (DW) begins. It could be that the UCA's are neither the source nor the result of the problem but just an intermediate in this whole issue.
Regarding the source:
It could be that the increase in mass of the new axle makes DW a problem where it wasn't previously. Is there absolutely anyone around that you could swap rims/tires with just to check if the tires are your source? IE your source could always have been there but just wasn't enough to set off a resonance.
Regarding the result:
Assuming you have a source that initiates the resonance, for whatever reason it seems to have fallen upon your uppers to do the work of damping it out. It could be the uppers are doing all they can but your frame rails themselves are not stiff enough. I believe I have seen where a trackbar brace or other between rail brace was added to stiffen up the frame as a box. @mrblaine you have added a support before to fix DW right?
Hail Mary:
I also had a bout with DW. When i did my JK axle swap i always had a shimmy of sort on certain one-wheel pothole inputs. It was there from the start when everything was brand new. It got worse when i went to 37's. My balljoints passed all the tests but when I pulled the knuckles they rattled back and forth easily but still didnt have up/down slop. I swapped out the BJs and hit the same pothole, no shimmy / DW. For reference, these were Spicer Balljoints which basically couldn't do the work even from the get go. Also note, i had bumpsteer so I was asking a lot.
Penance:
If all else fails, you can do what I did... cut it all off and go to Savvy Midarm. It's not like you'll regret going to a midarm either.
I knew there was a reason I liked you. 5000 dollar solutions to 10 dollar problems. You're just trying to make me feel at home away from FB where practically every answer is the same. Hey, my lower control arm slots on the axle are a bit worn what can I do? Oh, no worries, just cut them off and weld on all new mounts.Penance:
If all else fails, you can do what I did... cut it all off and go to Savvy Midarm. It's not like you'll regret going to a midarm either.
B00mb00m
The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
OP
OP
Ive tried caster at 4, 5, 6 and 7. John Currie told me they like it at 4.5-5 so that's where its at now.
And I'll bet good money none of those made any difference in severity or onset speed.
OP
OP
Well, we made it. No DW the 900 mile trip to Florida yesterday. Actually drives really well mannered at 70mph (except a slight steering wander from having the rear loaded down with vacation crap for the 10-day trip.
To ensure it was road-worthy for the trip, I tested it up and down the highway all day Friday hitting every bump i could. While doing so, I noticed an interesting phenomenon. The intentional binding of the arms keeps the DW at bay, which transforms it to more of a slight brief shimmy that corrects itself. Once at highway speeds (above 55) I notice that the shimmy is gone and is now presenting itself as bump steer. With this new observation in mind, I decide to try "the bump" at 55mph to see how it behaves. So i did-no shimmy, just bump steer.
So, thus far the results from hours and hours of tweaking, thinking, discussing with Blaine, and subsequent testing of potential solutions (as well as some WAGs):
1. DW above 30mph when specific bumps are hit.
2. No DW when UCAs are put in bind regardless of speed.
3. Same DW events induce a slight brief shimmy that corrects itself instead of DW.
4. Speeds above 50mph transform said shimmy to slight bump steer.
5. Shimmy only between 30-50mph when "the bump" is hit.
At no time during my 900 mile trip did the rig make me or my wife feel unsafe. It handled every event well regardless of the condition of the road, and we encountered much shitty "road work" areas between Ohio and Florida. Everytime I saw a bump that reminded me of "the bump", uneven pavement, or hole ahead and just knew DW was going to ensue, I gripped the steering wheel with both hands and...nothing, right over it with no problem.
By the end of the trip the rig had me confident in my work around for now. However, back to the think tank and testing lab upon our return from this trip. UCA binding is not a permanent solution to my rig's resonance sensitivity. Thanks @mrblaine for helping me get this far.
To ensure it was road-worthy for the trip, I tested it up and down the highway all day Friday hitting every bump i could. While doing so, I noticed an interesting phenomenon. The intentional binding of the arms keeps the DW at bay, which transforms it to more of a slight brief shimmy that corrects itself. Once at highway speeds (above 55) I notice that the shimmy is gone and is now presenting itself as bump steer. With this new observation in mind, I decide to try "the bump" at 55mph to see how it behaves. So i did-no shimmy, just bump steer.
So, thus far the results from hours and hours of tweaking, thinking, discussing with Blaine, and subsequent testing of potential solutions (as well as some WAGs):
1. DW above 30mph when specific bumps are hit.
2. No DW when UCAs are put in bind regardless of speed.
3. Same DW events induce a slight brief shimmy that corrects itself instead of DW.
4. Speeds above 50mph transform said shimmy to slight bump steer.
5. Shimmy only between 30-50mph when "the bump" is hit.
At no time during my 900 mile trip did the rig make me or my wife feel unsafe. It handled every event well regardless of the condition of the road, and we encountered much shitty "road work" areas between Ohio and Florida. Everytime I saw a bump that reminded me of "the bump", uneven pavement, or hole ahead and just knew DW was going to ensue, I gripped the steering wheel with both hands and...nothing, right over it with no problem.
By the end of the trip the rig had me confident in my work around for now. However, back to the think tank and testing lab upon our return from this trip. UCA binding is not a permanent solution to my rig's resonance sensitivity. Thanks @mrblaine for helping me get this far.
It is a test to try and isolate the deficient part. If you have double adjustable upper arms, you can back off the jam nuts, crank one arm slightly longer and the other slightly shorter to create bind to load the bushings and take some squish or play out of them. If that has an effect on the DW, then it points to the arms being an issue.
OP
UCA stands for upper control arm. When properly setting and adjusting your suspension, you want your CAs (control arms) to not be in a bind. At ride height with the arms installed but not tightened yet, you should be able to easily remove the bolts. You achieve this by adjusting their lengths until you can. You set your driver's side upper length to the right pinion angle you need without the passenger side installed, then install the passenger side arm set to a length that allows you to slide the bolt in easily. At this point your uppers are not in a bind at ride height.
When i said I put my uppers in a bind, that means I adjust one arms to the point where I cannot remove a bolt without adjusting it. It's putting preload on the joint when in bind at ride height. This is only a temp work around to make the joint tighter and the rig driveable. Should not do this long term as it will cause early wear/failure of the joint.
You got it mostly right. If you adjust one until you can slide the other side's last bolt in, they will still be in a bind. That is due to the springs being overhung past the axle tube centerline. That pushes down on the perch and essentially tips the axle forward. To alleviate the pressure, you need to jack up on the front of the axle after you have used 1 arm to set the pinion angle. Jack up the axle (I use the tie rod) until you can spin the bolt easily which tells you there is no pressure on it. At that point adjust the other side arm to length and slide that side's bolts in.
This all assumes rig is on level ground, axle on jack stands, springs in at ride height. If the springs are out, your way works perfectly provided the rig is at ride height with the springs out.
OP
Well, home safely. Just shy of 2000 miles on the trip and not one DW incident or threat thereof. Work around successful for the trip. Actually, the rig handled that trip like a beast--75-80mph with no vibes and motor smooth. My wife now trusts it to take us anywhere. However, she complained about the seats and says the long trips must be spaced apart lol. Lastly, the Flowmaster is coming out and stock going back in. Thought I liked the sound until I had to listen to it for 12 hrs straight.