Severe Shaking After Going Over Bumps

[dangerranger83]

I recently did a D30 SAS to my truck and all has ben well until now. I go down a city street that uneven or over simple railroad tracks at about 35 mph and when I do so, I get this severe death shaking in my front, kinda fells like your stepping hard on the brakes with a warpped rotor or like an earthquake is occuring. But I stop to look and all looks well. I will say when I do apply on my brakes I do get a little jerking due to them being used and having a few uneven spots but I have mashed on them before and never got something like this. Could a kinked brake line cause this or could bad well bearings be the cause? I dont have lower retainers on my coil springs either, could it be my coils are loosing contact with my lower mounts and when they make contact again, it causes this problem Im having. Right now I have her parked until I can figure this out, Im going to go check everything out that I can but hope somebody can help shed some light on this problem I am having.

 

[Sasquatch_Ryda]

This is a notorious problem with jeeps them selves...lol.

I had a 94 grand cherokee with a 4" lift in it. It did this like crazy when you hit a pothole or large bump, it would just about shake the wheel out of your hands.

The problem is the trackbar. It was too short, I put on an adjustable track bar and never had a problem after that.

How is your trac bar to drag link angle?

 

[dangerranger83]

They are parallel with eachother and both are factory ones that came off the same vehicle. Why would it just suddely start doing this though, I travel the same roads everyday and the same way? What exactly is going on and moving wrong that would make it do this? Could a flexing trackbar mount cause this? What exactly should I measure to find out what's wrong? I plan on making custom steering linkage this next spring but if this continues, it may have to happen sooner then expected. Sorry for all the questions, I would hate to put my life or somebody elses life in danger while I'm drive.

 

[dangerranger83]

I just remembered that the only thing that I have changed since my SAS was I inflated my tires to the correct pressure and that is when my problem began. After doing some reading, my toe in could be my culperate but now my tires have more bounce to them due to there being more pressure in the tires. That's the only reason that I can see why it has suddenly started doing this.

 

[4x4junkie]

You're experiencing the solid axle gremlin known as "Death Wobble". He can be a nasty one to get rid of from everything I've read and had experience with.

Like was said, check your track bar and it's mounts (a flexing mount is no good. Not just because of the wobble, but it can eventually fatigue and break too), check all your link mounts, as well as your shocks and their mounts as well. Improper caster angle can potentially aggravate the issue as well.

 

[legoms013]

My buddies Jeep grand cherokee had it bad after he put on a 4" lift. Me and him couldn't figure it out for a while.

It was a combo of not enough castor (due to stock arms)
Loose control arm bushings,
Shot tie rods,
Shot steering stabilizer
Over inflated tires
Improper steering geometry
Crappy track bar bushings
and insufficient drop on the drop pitman arm (had to buy the equivialnt of a SJ extreme drop pitman arm.

After we installed new lower, adjustable control arms,
Heavy duty adjustable trac bar,
Extreme drop pitman arm
deflated tires a bit,
new trac bar mounting bracket
steering stabilizer
and alignment

THEN it went away.

We replaced things methodically too, one item at a time and taking notes about how and when the wobble would occur and what triggered it

Was a nightmare to say the least.

 

[dangerranger83]

Well my trackbar became loose at the frame so I got that fixed plus I had aired up my tires earlier that day to what's recommended. Been wanting to take it over the same railroad tracks at a good speed but its either rush hour or like after work tonight, a train was running. My caster angle is where it should be. If it does happen again and everything is tight, then I'm going to say my tires may be over inflated. I'll find out tomorrow when I take her on some country roads to go hunting. Like said, just go down the list of things.

 

[legoms013]

Best method I've found is to have someone drive slow and turn the wheel back and forth very rapidly while another person watches the front suspension/steering linkages outside, following the vehicle to spot components that are loose or worn or failed.

Ultimately it comes down to two things:
Castor (less than 3.5 degrees seems to facilitate death wobble, 5 degrees usually kills it, but sometimes up 7 is needed. not sure what stock is)
and loose components (tie rods, bushings, ball-joints etc).

 

[dangerranger83]

I'm running 6 or 7 degrees on my caster and with my longarms, I can change anything in a matter of time with ease. Until I can test it furture, I'm not touching anything but will report back soon enough.

 

[escort_gts]

Hmm, I am running 3.6* and 3.7* caster on mine. Had the shop do the alignment for me I never experienced the Death Wobble, but I did put new ball joints and adjustable trakcbar. I did research on the DW before the swap. I didn't want any problems with it since its a DD. I used the Stock steering stabilizer at first and could tell there was less bump steer after replacing the stabilizer..

I would get a steering stabilizer and put a brace on the track frame mount.

 

[legoms013]

Steering stabilizers help, but they are just a band aid really, they only mask the problem so that the symptoms are much less noticeable. Its like adding another shock because you have a tire out of balance. Just have the tire properly balanced!

Main issues seem to be slop in the steering box, loose steering box, or slop in the track bar assemble somewhere (joints, or the way it mounts).

But more often that not its a combo of all that has been mention before and you just have to be very methodical with eliminating slop anywhere it occurs.

 

[dangerranger83]

Well so far so good after tightening the track bars mount to the frame mount. I'll put a brace on it soon but due to having a headcold, cold outside and other things comming up such as the holidays, I haven't been to motivated, I just drive her nice and easy and no off roading due to no front driveshaft and no where to wheel at. I may weld anotherbrace to the side of my trackbar mount to help the other one out from taking all the load.

I did notice today my aftermarket/universal CV rubber boot rubbing on my axle tube when I went to do my daily inspection. Need to find upgrade (or down grade?) to u joints. But a set of cv shafts are only $70 from autozone, never looked to see if they have ujoint ones. Chromos seem a bit over kill and over priced for my purposes.

Need to get new brake rotors, mine have finally got clean but still getting pedal feed back so looks like I have a warped rotor plus bleed the brakes again. May replace those now then later.

 

[escort_gts]

Might want to use the mount I sent you. It has the taper for the track bar and should work better, Just my opinion.

 

[dangerranger83]

The problem is, its to short, doesnt go down far enough. But Im going to make a longer down part and weld it to it to accept an eyelet mount instead of the TRE it has. Only problem is going to be the ability to bolt it up due to that part of the frame is boxed in and getting my hand in there is impossible.