03-21-2012, 01:58 AM
Join Date: Jan 2011
Location: Billings, MT
I have written Dan Noyes more than once about this.
This was my response on Dan Noyes' Facebook page (he is the ABC investigative reporter that did the story and facilitated the letter from his local representative and Congressman Waxman to the NHTSA).
It is all fairly simple with the JK.
The stock front trackbar bolts need to be torqued to 125 ft. lbs. Re-torquing them to 125 ft. lbs. needs to be part of the dealership pre-delivery inspection and part of the recommended maintenance at every oil change interval.
What happens over time with suspension cycling, road/tire vibrations, and the natural elasticity of metal, is that the torque specs back off a little on some jeeps.
Because Chrysler used stock trackbar bolts that are 14 mm instead of the 9/16" size bracket bolt holes, there is slop of the stock bolts in the stock brackets if the torque specs back off of 125 ft. lbs. Except for the very newest 2012 JKs, all the rest of the JKs have trackbars with bushing end bolt sleeves that are also 9/16"--large enough compared to the 14 mm stock bolts that there is slop when the torque specs back off from 125 ft. lbs.
With the amount of slop in the bracket bolt holes and the trackbar bushings, when the torque specs are less than 125 ft. lbs. it leads to violent, tear-your-front-end-apart Death Wobble with the right kind of trigger to throw the front end into that harmonic oscillation--like railroad tracks, poorly balanced tires, bridge seams, etc.
The stock steering dampener attempts to mask the looseness in the trackbar ends/brackets/bolts, but eventually, it fails prematurely.
The uninformed driver continues to drive the jeep with Death Wobble.
Multiple episodes of Death Wobble end up damaging most of the rest of the front end. The loose bolts oval/wallow out the trackbar bracket holes and damage the trackbar bushings. One or more of the lower ball joints fail, the tie-rod and drag link ends fail, the unit-bearings fail, the steering box fails, and the front upper axle side control arm bushings fail. It is not uncommon for the trackbar bracket welds at the frame and the axle to crack. I have seen brackets ripped clear off the frame and/or the axle when owners continue to drive a JK with Death Wobble.
In addition to the first simple solution of adding re-torquing the front trackbar at pre-delivery, and later, after every oil change interval, the second solution is for Chrysler to properly train their techs how to inspect for and diagnose the source(s) of Death Wobble. Unfortunately, Chrysler simply gives them a Technical Service Bulletin (TSB) to upgrade the steering dampener. They do not train them to follow an inspection checklist to look at the trackbar bushings, trackbar bracket bolt holes, ball joints, unit-bearings, tie-rod ends, drag link ends, steering box and sector shaft, control arm bushings, trackbar bracket welds, etc. The alignment specs also can aggravate the problem if there is too much or too little toe-in or caster.
A new TSB with a comprehensive inspection checklist should also consist of switching out the too small 14 mm trackbar bolts with 9/16" Grade 8 fine thread bolts that actually fit the brackets and bushing ends.
The new, heavy duty steering dampener eventually fails just like the original one when it can no longer mask the true source(s) of the Death Wobble.
Where the JK Death Wobble most often starts with trackbar bolts that aren't torqued to spec, and then is severely aggravated by stock bolts that are much too small for the stock bolt holes and bushings ends, the TJ Wrangler most often starts with the trackbar for a different reason.
The TJ Death Wobble most often happens because the frame side end of the trackbar has a tie-rod end instead of a bushing end (like the JK does). The tie-rod end is designed for rotational movement, but it does not allow side-to-side movement. However, when the suspension flexes in a TJ, the leverage of the trackbar against that end results in wearing out and destroying the end. That is why in the ABC story, the 4x4 repair shops/vendors quoted recommend a different design for the attachment at the frame side end. It addresses the problem of that tie-rod end design binding when the suspension flexes.
I could explain a lot more, but these are the basic issues at hand here. I am no engineer. I am just a weekend hobbyist, but most every engineer and mechanic/alignment tech who has read my explanations and inspection checklist agree that a loose trackbar on a solid front axle vehicle with coil springs and control arms will result in Death Wobble problems--even if the tires are perfect and the alignment within spec.
Again, Chryslers' response needs to be:
1- an update to pre-delivery inspection at the dealer to re-torque at least the trackbar bolts
2- an update to the recommended service schedule to include re-torquing the front trackbar at every oil change interval
3- a Technical Service Bulletin (TSB) that properly trains dealer technicians to do a thorough inspection of all the front end links, components, ends, bushings, steering, ball joints, etc., and to replace the front 14 mm trackbar bolts with 9/16" bolts. It should add inspection for proper caster and toe alignment specs, and it should include inspection of the wheels/tires as aggravating triggers to the Death Wobble. Only after the true source(s) of the problems are addressed, then the TSB would recommend the installation of a new steering dampener.
In spite of all this, you need to know that Death Wobble almost never happens on a properly maintained jeep--whether it is stock or modified.
His: 07 JK Rub 2 dri, 6 spd, 5.38s in Currie RJ 60s, 4.5" Trailmaster long arm with 99" wheelbase, 40" Xterrains on ATX Slabs, River Raider cage, RIPPd
Hers: 08 JK Rubi 4 dr, auto, 5.38s, Teraflex LA w/ORE/King coilovers, 37" STTs on WE beadlocks, RIPPd