Death Wobble - JeepForum.com
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post #1 of 58 Old 08-12-2021, 02:29 AM Thread Starter
juan_carlos__007
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Death Wobble

Alright I know it' been talked about before but wanted to share this with you. I have 2" budget boost with 31" tires and 17" moabs. Since control arm bushings were worn out I replaced them with core4x4 adjustable control arms to stock length. Replaced left side ball joints and couple tie rod ends like 2 years ago. Took it for an alignment check and tech said right bearing was bad which wasn't it was the right side ball joints and tie rod end which I replaced and NOW I have death wobble! Took it for alignment after my repair and balance tires since I did notice slight vibration which went away but still getting DW. My caster was at 5 degrees so I added a couple degrees by shortening the length of the top control arm and still getting DW. I also replaced the upper control arm bushings at axle side with rubber ones. The track bar bushings are good not torn but still original from 1999 and can see the axle flexing while turning steering wheel. Track bar bolts, bushing sleeves, and mounting holes on axle and body side are not elongated. There's some play in the steering gear box that's the next repair if new track bar doesn't fix the problem. Also noticed after tire balance vibration went away but DW got more sensitive. I'm running 35 PSI right now but will reduce tire pressure to 30 PSI and if that doesnt help will rotate tires. I'm guessing there's a tire thats out of round, It's pretty annoying that my WJ was running fine with the beat up parts but when the repairs were done it made it tighter and woke up the DW beast. I was thinking it getting an adjustable jks bar with KOR bushings but decided to go with this instead
https://www.core4x4.com/product/t4-j-wj-ftb1/
For a little more I get color of my choice and johnny joints. No more freeway rides until I get the new panhard rod.

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post #2 of 58 Old 08-12-2021, 04:16 AM
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Consider also a new steering damper. If you didn't replace the spring isolators with the BB, then that is probably worth doing too.
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post #3 of 58 Old 08-12-2021, 04:24 AM Thread Starter
juan_carlos__007
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When I did the BB the isolator seemed fine, and I just installed a new moog trail boss steering damper. Didn't do any difference, I forgot to mention it since I saw no change at all with it.

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post #4 of 58 Old 08-12-2021, 08:22 AM
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Do your Core CAs have Johnny Joints or rubber bushings? When I put in the Core CAs with JJ on one end, I got DW a couple times too, and it was worse at high 7 caster. I have IRO adjustable track bar with KOR bushings which may have helped some but it will still DW if I hit the left front tire with a nasty bump. Last time I got it, I was towing the camper and that was not fun.

While I think the JJs offer superior articulation which is good for trails and rocks, I suspect they are too harsh for highway speeds and contribute to the DW problem. Yes they articulate, but they don't flex or tune out the DW harmonics. I would dump my JJs completely if I could make the Core fit with rubber bushings.

Knowing little enough about vibration theory as I do, I can say that the DW harmonic is a function of spring rates and damping present in the suspension. JJs instead of rubber likely change both of those variables. Everything in the suspension/steering contributes. Changing the balance in any one part of the system (like new tie rods) can retune the harmonics and wake the DW.

If you still have your old UCAs, I might try swapping them in to see if that tunes out the DW.
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post #5 of 58 Old 08-12-2021, 12:02 PM
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Did you get your car tracked after you finished all that work on your suspension Juan?
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post #6 of 58 Old 08-13-2021, 12:48 AM Thread Starter
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Quote:
Originally Posted by GmanWJ View Post
Do your Core CAs have Johnny Joints or rubber bushings? When I put in the Core CAs with JJ on one end, I got DW a couple times too, and it was worse at high 7 caster. I have IRO adjustable track bar with KOR bushings which may have helped some but it will still DW if I hit the left front tire with a nasty bump. Last time I got it, I was towing the camper and that was not fun.

While I think the JJs offer superior articulation which is good for trails and rocks, I suspect they are too harsh for highway speeds and contribute to the DW problem. Yes they articulate, but they don't flex or tune out the DW harmonics. I would dump my JJs completely if I could make the Core fit with rubber bushings.

Knowing little enough about vibration theory as I do, I can say that the DW harmonic is a function of spring rates and damping present in the suspension. JJs instead of rubber likely change both of those variables. Everything in the suspension/steering contributes. Changing the balance in any one part of the system (like new tie rods) can retune the harmonics and wake the DW.

If you still have your old UCAs, I might try swapping them in to see if that tunes out the DW.
All four lower and upper control arms have polyurethane bushings, I just ordered yesterday a core track bar with Johnny joints we'll see how that goes when I install it on. Now that you mentioned the core 4x4 control arms I'm experiencing popping sounds on the floor board when I fully turn the steering wheel Allie way to locking position and reverse. They did come with spacers but none fit on the upper ones on the body side maybe if I'm able to put in washer on each the popping a or death wobble can go away. It''s amazing how harmonics have everything in tune in order to wake up death wobble. I can't imagine having death wobble while towing it must be quite the experience. I don't have any of my old control arms the bushings were really bad on them. Now with all the new parts I can feel bumps on the road like the tweeter cowl cover and other stuff in the cabin rattles. I don't mind feeling the road, DW in the other hand is what's pretty annoying. Now I know why newer vehicles have solid axles on the rear only.

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post #7 of 58 Old 08-13-2021, 12:52 AM Thread Starter
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Originally Posted by Delta0 View Post
Did you get your car tracked after you finished all that work on your suspension Juan?
What do you mean tracked like alignment checked or like race tracked? I haven't taken it to another alignment check my caster readings are from an angle finder that I place under the steering knuckles near the ball joint

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post #8 of 58 Old 08-13-2021, 04:53 AM
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Originally Posted by juan_carlos__007 View Post
What do you mean tracked like alignment checked or like race tracked? I haven't taken it to another alignment check my caster readings are from an angle finder that I place under the steering knuckles near the ball joint

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Yeah Juan, I should have asked, "Did you get your car aligned after you finished all that work on your suspension Juan?
Sorry.

When you took your caster readings, did you have your car on absolutely lever ground please?
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post #9 of 58 Old 08-13-2021, 06:37 AM
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Quote:
Originally Posted by juan_carlos__007 View Post
All four lower and upper control arms have polyurethane bushings, I just ordered yesterday a core track bar with Johnny joints we'll see how that goes when I install it on. Now that you mentioned the core 4x4 control arms I'm experiencing popping sounds on the floor board when I fully turn the steering wheel Allie way to locking position and reverse. They did come with spacers but none fit on the upper ones on the body side maybe if I'm able to put in washer on each the popping a or death wobble can go away. It''s amazing how harmonics have everything in tune in order to wake up death wobble. I can't imagine having death wobble while towing it must be quite the experience. I don't have any of my old control arms the bushings were really bad on them. Now with all the new parts I can feel bumps on the road like the tweeter cowl cover and other stuff in the cabin rattles. I don't mind feeling the road, DW in the other hand is what's pretty annoying. Now I know why newer vehicles have solid axles on the rear only.

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Death wobble is fun for sure.... But it isn't so much the live axle up front, it is the suspension style. In the old days leaf sprung live axles didn't do this, if it did I have never heard of it and have owned easily over a dozen leaf sprung live axle vehicles including Jeeps. It is the coil spring style front suspension that seems to be touchy to the integrity of the bushing at the many pivot points. If it makes you feel better brand new Super Duty Fords also get this, my first experience with it was in an old Toyota Land Cruiser on the highway. Having no idea what it was I was quite surprised by it I'll tell you what, it almost ended very badly seeing it happened going down 89A in the Arizona mountains.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
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post #10 of 58 Old 08-14-2021, 01:52 AM
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Originally Posted by cDee63 View Post
Death wobble is fun for sure.... But it isn't so much the live axle up front, it is the suspension style. In the old days leaf sprung live axles didn't do this, if it did I have never heard of it and have owned easily over a dozen leaf sprung live axle vehicles including Jeeps. It is the coil spring style front suspension that seems to be touchy to the integrity of the bushing at the many pivot points. If it makes you feel better brand new Super Duty Fords also get this, my first experience with it was in an old Toyota Land Cruiser on the highway. Having no idea what it was I was quite surprised by it I'll tell you what, it almost ended very badly seeing it happened going down 89A in the Arizona mountains.
Bad tyres cause death wobbles on cart sprung cars cD.
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post #11 of 58 Old 08-14-2021, 09:04 AM
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So you replaced the steering stabilizer AFTER the DW started? This front end needs a complete Shakedown again. Dont count on parts replaced two years ago being good unless you touch them today. Track bar replacement is a good start, although Im not sure I would go with jonny joints myself either. Need to know Exactly what caster readings are. A close swag on the driveway wont get you close enough. DW is just to sensitive sometimes. Why did the tech recommend a wheel bearing? Are you positive it is not loose or binding? Tire pressure is to high, I run 28 in the front and 26 in the rear myself. Try rotating the tires just for a test drive. Just brainstorming here......

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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post #12 of 58 Old 08-16-2021, 01:39 AM Thread Starter
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Just a quick update I decreased tire pressure to 32 psi and it made it more susceptible to DW so I return it to 37 psi. I believe the tires are causing DW, but they're not the root cause. I raised on a friends lift and we could not find anything loose, the knocking sound I was hearing is due to the upper left control arm bumping against the unibody because the original track bar pulls the axle to the left due to 2" BB lift. Track bar bushings are not torn or dry rotted, but they have way to much flex like 3/8" or a 1/4" off center under axle weight load. Adjusted the steering gearbox half a turn and my steering got way more responsive the steering play is gone. With my friend putting wj on reverse and intermittently applying the brakes I noticed the whole axle clunks positive caster I guess like 1/2" to 3/4" and it pivot on the bottom and swinging on the top. The rubber bushings I just installed on the axle side for the upper control arms have way too much play. Ordered some press in johnny joints from iron rock offroad that someone sujested on another thread. Everything is tight except for those two.

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post #13 of 58 Old 08-16-2021, 06:42 AM
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My death wobble after replacing every part in the suspension actually turned out to be a lightly dragging brake caliper. That **** was scary at 70mph
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post #14 of 58 Old 08-16-2021, 01:33 PM
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Quote:
Originally Posted by juan_carlos__007 View Post
Just a quick update I decreased tire pressure to 32 psi and it made it more susceptible to DW so I return it to 37 psi. I believe the tires are causing DW, but they're not the root cause. I raised on a friends lift and we could not find anything loose, the knocking sound I was hearing is due to the upper left control arm bumping against the unibody because the original track bar pulls the axle to the left due to 2" BB lift. Track bar bushings are not torn or dry rotted, but they have way to much flex like 3/8" or a 1/4" off center under axle weight load. Adjusted the steering gearbox half a turn and my steering got way more responsive the steering play is gone. With my friend putting wj on reverse and intermittently applying the brakes I noticed the whole axle clunks positive caster I guess like 1/2" to 3/4" and it pivot on the bottom and swinging on the top. The rubber bushings I just installed on the axle side for the upper control arms have way too much play. Ordered some press in johnny joints from iron rock offroad that someone sujested on another thread. Everything is tight except for those two.

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Your tyres will have a lot more grip at 32psi than they do at 37psi Juan.
The tyre contact gets shorter and narrower as you increase pressure above the pressure needed to get stated static loaded radius,

"pulls the axle to the left" may be part of your problem I' afraid.
What can you do about getting them lined up?

Last edited by Delta0; 08-17-2021 at 04:46 AM.
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post #15 of 58 Old 08-16-2021, 02:36 PM
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Quote:
Originally Posted by Delta0 View Post
Bad tyres cause death wobbles on cart sprung cars cD.
Not that I have experienced, I've been driving leafed 4x4's for 40 years many times on very bad tires. Wobbles and vibrations, yes. True death wobble, no. Death wobble is a result of worn components that could be exacerbated by bad tires, but bad tires are not the root cause of it.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
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