Death Wobble: A 21 month saga. FIXED!

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

pull the front driveshaft. drive around. put the front driveshaft back in, pull the rear shaft, drive around in 4wd with no rear shaft (front wheel drive)

also, have you put a square on the front axle tube to ensure it is not bent?

consider pulling your rear axle shafts and checking to see if they are bent.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Control arm mounts cracked, possibly?
Bad-from-the-box steering gear?
I'm grasping for straws here.

Rebuilt steering box went in about 6 months ago (on test drives in the last 18 months, no wheeling). If did tighten up the steering considerably and it still feels very tight, even better with the inner frame rail now plated but the DW persisted. I replaced the intermediate shaft (which was sloppy) quite a while ago. Steering was tighter but still had DW.

I wont say that is not possible that a mount is not cracked since I have not brushed them down to bare metal and inspected the welds but I have had the arms off a half dozen times and looked them over. No obvious rips in the metal on the axle or chassis side. Worth a cleaning and closer inspection just to be sure.

I know the straw grasping feeling...

John

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

I did drive it around in front and rear wheel drive some time ago by pulling drive shafts. I also swapped in spare shafts but to no effect.

EDIT: I never considered pulling the REAR axle shafts since its a Dana 44 thats been trussed for the last 4 years. The rear follows the front into DW and the whole rigs shakes like crazy both front an REAR. You might be onto something here. At least its a new direction.

In the last alignment (three weeks ago) the camber was L 0.3 deg R -0.2 deg which is within the stock spec so I assume the axle is not bent. I will straight edge the long side tube tonight just to see if its bent.

I am thinking Go-Pro to video whats going on might be in order.

Next Steps:
Check track bar, bracket and brace for the 20th time.
Do another round of feeling for something loose while having the wheel turned
Check the long side axle tube for bends
Clean off control arm mounts and inspect very closely
Go-Pro the DW to see if I can see what happening (gotta borrow one)
Pull the rear axle shafts. Check rear axle for bends.
Start working the caster-scrub radius to see if something closer to a stock scrub radius or HUGE amounts of caster will do anything.

Keep the ideas coming

Thanks

John

 

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

something has to be bent or loose.

I have driven jeeps with caster way out of spec and they do not do what you are saying.

do you have a lateral steering box brace? IE one that braces from the passenger frame rail across to the sector shaft.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

consider pulling your rear axle shafts and checking to see if they are bent.

The more I think about this, the more it sounds like a possibility. I know that I have an outer race on the driver side that fits just snug in the housing. I always use copious amounts red lock tite when I press it in (by hand, no hammer, just a block of wood and my hand). The housing is clean an not galled so it never has spun but its always been a worry. The splines on the shafts (rear stock D44, front Chromo D30 Superiors) are twisted (yeah on 31's) a small amount so I know there has been a LOT of torque (or shock) put through it.

I have a brand new set of Factory 10 chromo rear shafts sitting in the garage. Just need to press on bearings.

Never heard of a rear axle shaft causing DW but this is an easy one to test and the new axles need to go in anyhow even if I end up getting a new chassis. Nothing lost by trying.

John

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

something has to be bent or loose.

I have driven jeeps with caster way out of spec and they do not do what you are saying.

do you have a lateral steering box brace? IE one that braces from the passenger frame rail across to the sector shaft.

I do not have a steering box brace. Never really wanted one since I have seen a couple of rigs with the ears broken off that had the brace. Assumption is that the horns flex, the brace pulls and snaps off the ears. Though I have also been told that this does not happen after a track bar brace has been installed (which I have done). Not sure what to think.

Rustys sells them for $59

http://www.rustysoffroad.com/rustys-steering-box-brace-xj.html

Have you run a steering box brace with no problems?

John

 

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

I do not have a steering box brace. Never really wanted one since I have seen a couple of rigs with the ears broken off that had the brace. Assumption is that the horns flex, the brace pulls and snaps off the ears. Though I have also been told that this does not happen after a track bar brace has been installed (which I have done). Not sure what to think.

Rustys sells them for $59

http://www.rustysoffroad.com/rustys-steering-box-brace-xj.html

Have you run a steering box brace with no problems?

John

Ive had the rusty's steering box brace on for about 4 years.

both with and without frame plating.

no issues.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

The brace is probably a good idea before things start to get bad (after preventative plating). I dont think it would wise at this time IF this is a frame flex problem.......

You definitely have me thinking hard about this.

There was a pretty good thread back in August on frame plating and braces:

http://www.naxja.org/forum/showthread.php?t=1031430&highlight=steering+box+brace&page=4

The focus of the thread is mostly on where and how to plate and various brace types to prevent frame cracking. Plating as I have partially done (inside, outside and bottom) from the front of the frame horn to the lower frame rail is the best way to do it when used in combination with a bumper that ties the two frame rails solidly together at the front.

I have been running a stock front bumper so the rails have never been tied together at the front. The outside of the frame rails and the bottoms have been plated in 3/16th for several years now. I have only just recently (last week) plated the inside of the driver side frame rail from the front of the rail back to the motor mount.

As Cracker said in the thread above the track bar and steering box work in opposite directions, one pulls, the other pushes (or vice versa) causing fatigue and cracks between them.

Lets ASSUME that the DW is caused by a weak frame rail on the driver side that can not restrain the steering forces, allowing the frame rail move around with the ensuing DW. I dont think installing a steering box brace at this point is going to restrain the frame rail sufficiently and stop the DW. The brace will just put loads through the steering box over to the passenger side rail and might break the box ears. This is not a problem if the rig is not suffering DW and does not have frame rail damage, which I am assuming I have for this discussion. I need to get at the root of the problem and stop the frame rail from moving around (if that is what is happening).

I have three options for stiffening up the frame at this point:
1) Plate the inside from under the motor mount back to the lower frame rail.
2) Add a bumper that ties the front frame rails together.
3) Add additional bracing over the top of the engine (way too much work).

If there is a crack near the motor mount/track bar bracket the driver side frame horn could be moving. A well tied in bumper would definitely restrain frame horn movement. Plating over the inside of the frame rail from the motor mount on back would also restrain the frame horn and solve the crack problem (I assume any crack is either under the motor mount on the inside or under (actually above) the plate I added to the bottom of the frame rail).

Being lazy the bumper is the easiest thing to do first when I am ready to stiffen the front frame rails. Plating under the motor mount is a pain but I would consider it a last resort after exhausting other options.

Getting some video of whats happening down there may prove to be key.

John

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Gave all the fasterners for the track bar, track bar bracket, track bar bracket brace and steering box a check with a 24 inch breaker bar. Everything took a little bit of tightening but not much. I could feel the yield point coming (if you do this a lot you know what I mean).

Went for a drive. Still have DW. I could feel it building as I accelerated from 25 up to 45 mph. Did not feel that on the last two test drives. It just screams that this is a tire problem. Thought I alread checked that with "new" used tires and NEW rims plus a tire swap. The bad thing about this is that maybe I have bad tires PLUS something else that I fixed AFTER the tire swap.....The possibilities are endless.

Straight edged the long side tube after polishing it up underneath and checking the straight edge on a piece of glass. Long side tube definately bent upward about 1/8 inch towards the outside. Put a inclinometer on it. Inclinometer read 0 when pushed over against the differential. Push the inclinometer over against the passenger side lower control arm mount. It read under a degree, maybe a half degree of negative camber on the driver side. Hard to read such small values. This fits with the camber being 0.5 degrees different left to right but thats a bit more than the 0.2 degrees negative on the passenger side that I got from the last couple of alignments.

More to come.

John

 

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

Get your tires balanced.


Put some torque seal on your trackbar and steering box braces. Drive around, see if it breaks anywhere

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Will do. Thanks for staying with this.

John

 

[mayub78]

Re: Death Wobble: An 18 month saga. Need help still

Hello there, I have a 97 Xj, and when I bought it, it had been crashed from the driver site and the fram rail was not in a very good condition, so I installed some frame stiffeners on the outside, and installed a steering box brace, drove it for a long time then stared to have the DW problem, fist I chanced the track bar, and it stopped for some time, the it stared again, the track bar was practically new, checked for loos parts and everything seem to be ok, so I borrowed a friends Go-Pro, took it for a ride, after watching the video, everything seem ok, but when I payed attention to the steering damper, I could see that it wasn't doing what it was suppose to do, help to dissipate the tire movement on the steering wheel, I exchange it for a HD one from Old Man Emau and my problem was solved.

At your second picture, it seems that the bushing that holds the steering damper to the drag ling is or worn out or loos.

Hope this helps.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

mayub78:

You are very observant. While I did put in a new damper after all this started 18mo ago it is now shot. You an easily stroke it by hand. The damper can mask the problem but it purpose is to reduce the shock felt in the steering wheel when you hit something, not to prevent DW. I could replace it but the damper is not the cause.

rockclimber:

You sir are a genius: You insisted that something must be broke or bent. Looks like you were right. KISS (not not kiss, KISS: Keep It Simple Stupid)
The VP of our local club (Northern Virginia Jeepers Assoc) dropped off his Contour (like a Go Pro) tonight. While here I had had him turn the wheel back and forth while feeling everything in the suspension and steering. Done this a dozen times over the last 18 months but its the tried and true method.....

Ball Joints: Good
Unit Bearings: Good

As soon as I touched the steering gear you could tell something was wrong.

TRE on drag link at steering box: Good
Steering box to frame: Good
TRE on drag link connecting to the tie rod: Good
TRE on drag link at passenger side: Good
TRE's on the driver side of the tie rod: Good
Axle end of the Track Bar: Good
Track bar bracket end of the track bar: MOVEMENT=BAD. It moves about 1/8 inch in and out for a total of ~1/4 inch. The joint is crazy tight but if the delrin is hammered out its not going to grip the ball properly and restrain it.
Track bar bracket to frame: Good

I just did this same test about a couple months ago and there was nothing wrong with the track bar. Remember my comment about chasing my tail? Well that may now be what is going on. One of the very first things I did when this started so long ago was to rebuild both ends of the RE1660 track bar. That did not solve the problem. It is perfectly plausible that while testing the rig I hammered out the new delrin bushings on the frame end of track bar before I found the original problem and solved it but by then other things were messed up like TRE's and they got replaced. So now I find that I have ONE part thats obviously bad.

Could it be this easy?
Calling RE in the morning to see who sells the right part. Stupid RE website does not give the part number for the rebuild kit for that flex joint anymore.

John

 

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

4 wheel parts will have it.

I have had a number of people I know running that trackbar have issues with that joint.

it is simply too small. consider selling/ditching that trackbar for one that runs either a 7/8" heim (or greater) or a 2.5" Johnny joint.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

The HP F250 D44 (Chromo, Hi Steer 1 ton, CTM's) that is sitting on the garage floor has a 7/8th Heim on it. As soon as the DW is fixed (so I know the chassis isnt wasted) this axle will go in. Totally agree on the RE superflex joint being too small. They did upgrade to a 1/2 inch joint (I ordered a whole new end) from 10mm (what I had). The part wont be here until Tuesday. I wont drive it until then. No point. I know what it will do and now that I know for sure that I am causing additonal damage as I test the vehicle I am going be extra cautious.

I will follow up next week.

John

 

[cracker]

Re: Death Wobble: An 18 month saga. Need help still

3/4" rod ends work all day long....run them that way on the buggies and the MJ.

 

[blondejoncherokee]

Re: Death Wobble: An 18 month saga. Need help still

I run 7/8x7/8 hiems on the track bar and drag link with 3/4" misalignments and 7/8x3/4 on the tie rod. I like it . All ruffstuff. all 3/4" fine thread grade 8 hardware. Seems pretty beefy so far.

 

[irish1371]

Re: Death Wobble: An 18 month saga. Need help still

You said it dove across the lanes while in DW? Had the same issue.

my pass side caliper piston was hanging up causing dw then progressed into insta lane changes and horrid dw

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Well the camera was sitting there. I could not leave well enough alone...

Welded some exhaust tubing to the frame rails to use as a camera mount.....


First is a shot with the camera mounted to the front panel between the frame rails...
http://s49.photobucket.com/user/nosigma/media/DWRun1DW12_0001_zpsf660a733.mp4.html

Here the camera is mounted to the track bar brace which is welded to the frame rail on the pax side and the track bar mount on the DS along with being bolted.
http://youtu.be/dM_z4aGPef4

Finally here is the view with the camera mounted on the driver side exhaust tube "horn"
http://www.youtube.com/watch?v=NvSo9EtZxGc

 

[cemeyer]

Re: Death Wobble: An 18 month saga. Need help still

In the 3rd video, when you are sawing back and forth, your trackbar to frame joint is moving and if you watch closely, it appears that the frame is also flexing. The frame has to be cracked somewhere.