Shake, Rattle, and Roll

[FrankenJeep]

The dreaded "death wobble", a subject often seen here! Mine is afflicted with it-..has been since I got it 8 years ago. I replaced the tie rods and ends. Helped a lot. Didn't stop it entirely. Haven't checked the box to see if it can be tightened. Instead of 25 MPH, I can now make 35! So what else should I replace or rebuild. I have the bell crank rebuild kit. its time to make this Jeep so I can keep up with traffic. Any suggestions?

FJ

[Joe Gopan]

Sounds like your steering knuckle bearings are due for attention.

[skyjeep50]

Stopping death wobble is not entirely a matter of replacing parts. It is making sure the entire steering system is free of excess wear and "slop" in movement and setting the correct bearing pre-load for the steering knuckle cap bearings. New knuckle seals also help. The bearing pre-load helps damp out feedback motion induced from road bumps. The steering gear itself can't be "tightened". Yes, there is a big nut on the outside that you can screw in - but it's not there to tighten anything. A good read of the technical manuals for your jeep will help!

[Joe Gopan]

Steering knuckle seals have nothing to do with prevention of shimmy, they are the last component added to steering knuckle after assembly and precision adjustment. Worn bearing caps, worn bearings/races, and improper shim adjustment are major factors.

[skyjeep50]

Bearing pre-load is measured without knuckle seals installed. When brand new, correct, military knuckle seals are installed on a M38 after bearing pre-load is adjusted to spec - you can measure a further increase in resistance to movement of the knuckle. Worn out seals don't press on the knuckle ball as much as new seals will. I'm not talking about the felt seals used on early CJ's, the seals on military jeeps are rubber pressed to the knuckle by a spring strip and they do get old and wear out. I don't have the numbers but I could certainly feel the difference on my M38 and M38A1 when I rehabbed the steering to get rid of wobble. The resistance to movement is what helps damp out unwanted steering system wobble. New seals are not the primary means of stopping death wobble - but they do contribute to the solution.

[Fortyeight2A]

I didn't have death wobble on my '48, but I had 270 degrees of slop in the steering wheel. I replaced the kingpin bearings and eliminated 180 degrees of slop. I replaced the bushings and sector shaft in the Ross box and eliminated another 45 degrees of slop.

[Joe Gopan]

And remember, the precision preload adjustment for the steering knuckle shims is done without the wiper seals in place.

[artificer]

I suggest spending 15 minutes to ensure the steering system is properly diagnosed before going on a shotgunning exposition.
It is quite possible the problem may a combination of any number things & may just happen to include swivel pin bearing wear or adjustment. We just don't know!

Death wobble can be any number of things [exacerbated by bad wheel balance].
1. Check tyre pressure
2. Wheels on the ground
3. Is the steering box full or MT?
4. Have someone @ the steering wheel see if they can it lift in & out [toward & away from themselves].
5. Have them rock the steering 'wheel' back & forward. How far does it move before the pitman [drop] arm moves
6. Is the steering box sector shaft [pitman arm mounts on] moving in & out or up & down [sloppy] when they are turning the steering wheel
4,5 &6 indicate steering box wear, bushes, bearings & adjustment issues
7. Have them rock the steering wheel hard & check:
[a] pitman arm movement
both adjustable ends of the drag link for movement
8. Still rocking check all ball joints [tie rod ends] for movement
9. Check movement issues around the bell crank
10. Jack front end so wheels are about 25mm off the ground & place vehicle on stands
11. In the straight ahead position rock LHF wheel in & out as if turning. Check where there is any movement
12. Grasp wheel top & bottom & rock in & out. Movement?
13. Helper applies brakes....movement reduced or eliminated indicates wheel bearings need adjustment
14. Remaining play is swivel pin bearings [king pins]
15. Do exactly the same on RHS.

One will have found all movement [there should be none], fixed & eliminated ALL their problems & it will probably be more than one thing, that's for sure....bell crank is one usual major contributor besides swivel pin bearings.

[Joe Gopan]

One can almost count on bad Shimmy being due to worn Steering Knuckle bearings. They are one of the most ignored items on a Jeep.

[artificer]

One can almost count on bad Shimmy being due to worn Steering Knuckle bearings.

That may be so, but is not the point!
Who on this forum knows in this & other cases swivel pin bearings are the problem.

Anyone who professes to be a 'mechanic' should not be guessing, as the quoted comment is clearly doing, but diagnosing issues properly.
A combination of simple things can be very easily eliminated using a checklist like has been offered [called diagnosis].
Much easier & preferable to guessing & going off on some tangent pulling things like swivel pin bearings apart, on a whim.
What happens after all that work doesn't fix the issue or the collective total problem?

[Joe Gopan]

No guessing, 60+ years hands on Jeep service experience is a pretty good background, the steering knuckle bearings are on a one way trip after Jeeps leave the showroom, they require regular servicing by skilled mechanics that rarely happens on time. And John, the only way to tell the condition of the cups and cones is to disassemble the steering knuckle to clean and inspect their condition. The only way they get proper lubrication is to clean and hand pack them.

[artificer]

No guessing 60 Years of doing the same thing

What happens next when what is guessed, doesn't fix the shimmy & it's still there?
What does one tell the customer?
Do they get charged for the non fix?

after all that [swivel pin bearing] work doesn't fix the issue or the collective total problem?

Could very well turn out the steering box has no oil, internal bearings & bushes are worn & it's way out of adjustment plus a spring in the drag link is broken.
Joel obviously missed what I indicated about swivel bearings

That may be so,

I have made a positive contribution to fault finding/diagnosing/troubleshooting what is causing this shimmy & it's not guessing! End of story & it's up to the OP to decide what is the way to go about this. Remembering when the swivels are all pulled apart one can't check any of the other parts suggested in the earlier 15 minute checklist.

[Joe Gopan]

The "Chicken or the Egg", John. Jeep experience has a way of sorting that out in minimum time. How about a 60+ year checklist John?