Death to the Wobble (1 Viewer)

[Azrocks]

Join in my journey to figure out what is going on with my FJ40 and it's newly acquired death wobble. I haven't done all the stuff to check it out but that's half the fun. Let's guess what the heck is going on here.


Starting Point.
OK, here's the deal. I was running 31x10.5's on my 79 FJ40. It had a previous lift from the PO that was about a 2" or so lift. There were already shims installed front and back. I could run 75 mph easily on the freeway (sbc 350) and it tracked great. No problem whatsoever.

The Change.
Keeping the original shackles, I installed a 4" Hell Creek lift. I then ditched the 31's for Mickey Thompson 35" bias Baja Claws that were on my old rockcrawler (which could run 75 on the freeway as well). The tires have been in a shop in the corner for about three years (in the shade, no sun). I reinstalled the shims front and back. In front the thick part of the shim is facing towards the front of the vehicle.

The Symptom.
After the lift and installation of the tires I now have a serious death wobble starting at about 25 mph. I can either brake hard to stop it or I can power through it and then be OK up from there on (going straight, haven't tried any curves at speed.

Attempted (and failed) Cures.
- ran with shims in and out.
- swapped tires front to back and back to front
- jacked both tires up in the air and gave the tires a good shaking. No play.
- adjusted toe in to about 1/4"
- deflated tires to lower pressure.
- inflated tire to higher pressure.
- gave all the steering components a really good shaking and have no perceived play
- front driveshaft has a loose ujoint, which was there before the lift. I'm running in 2WD.
- driven with back tires high pressure, front low then front high and rear low.
- If I put a 12" in flat stock across the knuckle studs and put a level on it, the level shows the bar is tilting down towards front of vehicle a bit. Not sure this it the correct way to measure caster.
- Installed 6 degree shims in front.
- made sure lug nuts were compatible with my rims and seated correctly
- made sure rims were seated flush
- replaced steering box
- replaced tie rod ends
- got 35's balanced along with airsoft pellets
- tighten up ubolts just to make sure.
- replace spring pins and shims
- rebuild knuckles (made a noticable difference)
- steering stabilizer (helped enough to make vehicle drivable, still some wobble)


Stuff I'm going to try.
- break down and buy new tires.




Well, any bets, guesses, and/or suggestions as to what's causing the dreaded DW?

 

[KOOTENAY KRUZER]

I think the front shims should have the thick side to the back. If the flat bar measuring trick is valid then I think it should tilt up towards the front of the vehicle. Think of the angle on bicycle or motorcycle forks - that is positive caster, which is what you want to stabilize your steering.

 

[toyotated]

Sounds similar to the problem I am having. I have a SOA lift and running 36" TSL SX's with 10" wide steel wheels. I originally had the tires mounted on 8" wide steelies and used balancing beads to balance the tires with little or no death wobble at highway speeds. Now since I have swapped them to the wider wheels I have slight death wobble at 100Km/h (60MPH). After eliminating all the other problems like you have I am thinking the balance of my wheels could be the culprit. I am using balancing beads but from what I have read the proper way to balance a large tire like mine (especially bias ply) is to mount the tires and put them on a balancer and spin them up without the beads in them. Then add weights as the blancer requires. Next break the tires back down, add the balancing beads and remount the tires again. Now you should be ready to roll. I plan to try this soon and see if it makes any difference. A friend of mine just did it with the same tires on his Heep and they track straight as a whip! I got this info from my friend after he says he researched it long and hard and swears it cured his problem. I am hoping it cures my problem as well. If this doesn't work for me I am going to go back and check my shims on the knuckles again although I was pleased with the setup when I rebuilt them a while back. Also might splurge and get a proper wheel alignment done even though I set the toe in to about 6mm.
Maybe someone else can chime in with their opinion on how to properly balance a large bias ply tire? The above method seems to make sense to me but I am sure there are differing opinions.
Azrocks, I am watching your thread with interest to see what you figure out with your Cruiser.

 

[jmylie]

I'm guessing two issues.

Tires out of balance. I would go with dyna-beads or the like versus the old style lead weights.

You just switched from 2" of lift to 4" of lift and 31" tires to 35" tires.

35" tires are heavier putting more stress on your tie rods steering components and the added lift will change the caster. The old shims may be the wrong angle to correct the caster.

My understanding is to measure caster without shims. If caster is -6, then you need 6 degree shims to bring it back to zero.

Also check your center arm for the steering, it may need to be tightened up do to the larger tires.

 

[Hugh Heifer]

I think the front shims should have the thick side to the back. If the flat bar measuring trick is valid then I think it should tilt up towards the front of the vehicle. Think of the angle on bicycle or motorcycle forks - that is positive caster, which is what you want to stabilize your steering.

Nope. Pretty sure this was addressed a bit ago. Fat side forward was the outcome of that thread. There is a bunch of stuff about caster and death wobble in the faq.

 

[KOOTENAY KRUZER]

I just checked my BJ42 with SOA - the caster shims are thick side to the rear and there are no issues with steering, this thing steers and tracks better than my other trucks did brand new off the showroom floor. I think you find you need a certain amount of positive caster (top of the king pin is slightly behind the bottom of the king pin) for steering stability and once you modify a vehicle any shims you need will be to adjust the amount of positive caster - to much positive caster can make it track very well but be difficult to steer, to little leads to steering instability (death wobble). Where the thick end of the shim goes probably depends on each individual vehicle's modifications.

 

[AKcruiserfreak]

Check that your rims are mounted flush. I found that mine were not flush due to the retaining screw on the drums, now I have no death wobble.
Also, the thick part of the shims are always facing forward unless you did a shackle reversal or some other silliness.

TK

 

[Shipwreck]

I just checked my BJ42 with SOA - the caster shims are thick side to the rear and there are no issues with steering...

KOOTENAY - SOA is the difference between your rig and the Azrock's rig. On a SOA configuration, spring shims go thick side to the rear while on a stock spring under axle, shims go thick side forward to increase caster.

Azrocks, to diagnose death wobble you need to first make sure everything that locates your wheels under the truck are tight and have no excess play. Start from the frame and work toward the tires. That includes spring eye bushings, U-bolts, trunion bearings wheel bearings, lug nuts, etc. Then follow your steering linkage from the steering wheel through the steering box, relay rod,tie rod, rod ends and steering arms. Finally check caster, wheel balance and warped rotors or drums.
In my experience,death wobble is often caused by a combination of many different things, but a slight change in one issue may tip the scale so that the wobble manifests itself.
good luck - let us know what you find...

 

[atazman]

Death Wobble Problem

Here's what worked for me after exhausting lots and lots of other possibilities. I increased the knuckle bearing pre-load to about 12 lb. End of problem.

Just a reminder that wear in any of the tie rod ends can cause the problem too. Check for any "slop" in the steering.....check that your spring bushings are in good condition and the shackle bolts not too loose. Another possibility....worn/loose steering box internals.

 

[Hugh Heifer]

KOOTENAY - SOA is the difference between your rig and the Azrock's rig. On a SOA configuration, spring shims go thick side to the rear while on a stock spring under axle, shims go thick side forward to increase caster.

Azrocks, to diagnose death wobble you need to first make sure everything that locates your wheels under the truck are tight and have no excess play. Start from the frame and work toward the tires. That includes spring eye bushings, U-bolts, trunion bearings wheel bearings, lug nuts, etc. Then follow your steering linkage from the steering wheel through the steering box, relay rod,tie rod, rod ends and steering arms. Finally check caster, wheel balance and warped rotors or drums.
In my experience,death wobble is often caused by a combination of many different things, but a slight change in one issue may tip the scale so that the wobble manifests itself.
good luck - let us know what you find...

Great advice.

Here's what worked for me after exhausting lots and lots of other possibilities. I increased the knuckle bearing pre-load to about 12 lb. End of problem.

Just a reminder that wear in any of the tie rod ends can cause the problem too. Check for any "slop" in the steering.....check that your spring bushings are in good condition and the shackle bolts not too loose. Another possibility....worn/loose steering box internals.

Questionable advice.

REALLY GOOD ADVICE <<<<< LINK

 

[TLCHopII]

HAd a similar, recent, experience. the nuckle steering horns "came loose". re-torque & align...no further issue.
37, sua, shackle reversal, 3.5" lift primarily due to the reversal,35/14.5x15 on mag.s

Best of luck with yours

 

[Azrocks]

Thanks for all the replies. Hugh H, I've read the link you posted. That's where I am getting a lot of my proposed solutions.

The strange thing with all this is that if I power through the DW, I can make it "go away". Weird.

I picked up some 6 degree shims yesterday that I'm going to put in Sat. The rig seems to be darting around quite a bit so I'm thinking its either the 4 degree shims aren't enough to correct caster or I've really got some slop somewhere in the front end.

On we go......

 

[Liam]

i would definitely go with ceramic beads to balance those tires. I had a death wobble when i put 34" SS on, but then i switched to ceramic beads and it completely went away.

 

[Azrocks]

How many did you use. Any kind in particular?

 

[Pin_Head]

The fat end of the shim points to the shackle to increase (positive) caster.

Since the problem started when you changed springs, I would start there and check the U bolts and shackle pins for tightness.

1/8 inch toe end is best.

Two factors contribute to wobble:

1. Problems with wheel alignment

2. Problems with slop or play in any component that locates the wheel, from the steering box, linkage, springs knuckles wheel bearings and rims.

 

[Azrocks]

OK, I installed the 6 degree shims and while it seemed to track a little bit better, I've still got the wobble. I had high hopes because the shims that were already installed were only 2.5 degree.

I was looking around a thought maybe the lug nuts weren't seated all the way. Tightened them down. Still shaking like crazy.

Bummer

 

[Azrocks]

Check that your rims are mounted flush. I found that mine were not flush due to the retaining screw on the drums, now I have no death wobble.
Also, the thick part of the shims are always facing forward unless you did a shackle reversal or some other silliness.

TK

Checked out. I've got discs in the front. Rims seated flush.

 

[Azrocks]

OK, I pulled all my rod ends off and will replace them next. In the process I found that my steering box has a little play side to side when moving the pitman arm back and forth. I'm going to see if I can get another through the warranty.

If I bring my tie rods into a checker or napa, can they tell what the tie rod ends are by looking at them? If not, what's the best way to tell what I've got?

 

[Liam]

How many did you use. Any kind in particular?

i cant remember the website, i think it is innovativesolutions.com. You can also search on mud for ceramic beads...

i think i used 12oz....

 

[Azrocks]

Thanks for the reply. I think I'm going to go cheap to start with and try Airsoft pellets and see how they work. I just want to eliminate that variable.