Front end shakes at high speed?

joebuck · Posted: Wed Oct 22, 2014 3:11 pm Post subject: Front end shakes at high speed?

Frequently my front end shakes or wobbles when at high speed. I touch the brakes and it stops. How can I stop the shimmy please
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1952 M38

joebuck · Posted: Wed Oct 22, 2014 7:23 pm Post subject:

Found it! Well found an old thread
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1952 M38

ACRay · Posted: Wed Oct 22, 2014 7:44 pm Post subject:

You have "death wobble" ? Hotty Toddy!

wilfreeman · Posted: Wed Oct 22, 2014 11:00 pm Post subject:

Rebuild everything. Seriously, check tire pressure, wheel bearing adjustment, steering gear adjustment/looseness, drag link adjustment, bellcrank looseness, all tierod ends. Use the manual to adjust to spec and rebuild if worn out.

Also, don't forget the obvious - alignment and wheel balancing.
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Matt
1953 M38a1
1964 USMC M38a1
'51 USMC M100 trailer, '54 M100 trailer, '90 M101a1 trailer
Http://wilfreeman.wordpress.com (M38a1 build blog)
http://m38a1usmc.wordpress.com (USMC M38a1 rebuild blog)

wesk · Posted: Thu Oct 23, 2014 1:17 am Post subject:

And set preload on king pin (steering bearings) using a spring scale IAW the manual.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

joebuck · Posted: Thu Oct 23, 2014 6:59 am Post subject:

I keep my jeep at hunting camp 90% of time so I rarely go over 20. But have it home now taking kids to school which they love and I do too since it is so nicely restored. So I have some road miles on it now and I noticed it shakes a lot more in 2 wheel drive than 4 wheel drive ? If that hints the problem?
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1952 M38

ACRay · Posted: Thu Oct 23, 2014 7:10 am Post subject:

I'm not a steering geometry expert, but death wobble is a huge thing with lifted Jeeps like my 06. I had to really get the agles right, everying tight and beefy enough to handle 35s at 80 on the interstate without it coming apart. With your resto I'd start checking for worn steering compnents from end to end, lube it all and tighten everying thing to spec. Since yours isn't some big rock crawling I'd bet there's just some little someting lose in a spot.

whydahdvr · Posted: Thu Oct 23, 2014 7:49 am Post subject:

Throwing in my 2 cents experience with the wobble at higher speeds. My situation turned out to be the alignment. I took it to my local tire shop, gave the manuals and Wes's guidance, and they found that my toe-in was out by 0.5*. The balance was also off on all the wheels and by a lot on 1 or 2.
Bottom line for me was the alignment. After I had that done it drove beautifully at about 50, which dismay max speed unless I'm going down a good hill with a tail wind!
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North Shore, MA
Santa Fe, NM
1942 GPW
1952 M38
1964 Apollo 5000 GT

De Opresso Liber

joebuck · Posted: Thu Oct 23, 2014 7:51 am Post subject:

For those following along with same problem...i found an old Wes ( no pun intended) reply that i think is definitely going to help me narrow it down.

Wes replied:

Sometimes a professional front end inspection will quickly ID the source of the problem and save you a lot of shot gunning troubleshooting time and material loss.

I've been at this for 50 years and a quick check of a closed knuckle 4wd front end is very simple and takes very little time and no special equipment.

The list of causes for the death wobble is very short.

1-King pin bearing wear resulting in a looseness that becomes very apparent at certain speeds and when aggrevated by a bump. Usually a hard shot on the brakes will stop it. Occasionally you have to come almost to a stop to stop it. To inspect their condition you simply raise the jeep and grasp the top and bottom of the tire and rock it. If it moves fix the king pin bearings.

2-Heavy steering component looseness. Usually the tie rods and bellcrank will show their looseness all the time. It is the drag link and pitman arm and steering gear box that can hide a loose issue and then let it suddenly appear at certain speeds or after a bump as a death wobble. Again raise the jeep and lock the steering wheel down and check all components for looseness. Fix the worn part.

3-You hear balance brought up a lot but balance does not cause death wobble. An out of balance condition will result in wheel hop (vertical motion) that is transmitted as a vertical hopping sensation though the floor. It is tire tread and sidewall damage that can cause a wobble tracking of the tire at certain speeds being more pronounced then others. This can be tough to isolate and generally swapping in a pair of known good front tires is the best way to troubleshoot this problem.

Remember when the tires are on the ground you should only be able to rotate the rim of the steering wheel 1/2 to 3/4 " side to side with no movement of the tires.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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1952 M38

joebuck · Posted: Thu Oct 23, 2014 8:12 am Post subject:

"Remember when the tires are on the ground you should only be able to rotate the rim of the steering wheel 1/2 to 3/4 " side to side with no movement of the tires. "

My steering wheel with tires on the ground has 5" of play!!!!! oh lord
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1952 M38

joebuck · Posted: Thu Oct 23, 2014 12:53 pm Post subject:

1. Check tire off ground...doesnt wobble or have slack for king pin
2. check all components and nothing seems loose or move except steering drag link and steering drag link will rotate a little bit here the picture

3. Could i tighten screw in steering box?

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1952 M38

joebuck · Posted: Thu Oct 23, 2014 5:32 pm Post subject:

Took it for a spin. Really bad death wobble in 2 wheel drive at 38mph and not as bad in 4 wheel drive. Been 60 mpl in 4 wheel. I can touch brake and disolve it quickly in 4 wheel but 2 wheel scares me

All my rods and bars are tight. My left front tire has a hair of a wiggle on king pin. Right tire is solid

Steering wheel has 5 inch slack in it with tires on ground.

So I thinking no mechanical but get an alignment and tires rebalanced or is steering slack the cause?
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1952 M38

wesk · Posted: Thu Oct 23, 2014 7:51 pm Post subject:

4x4M38 · Posted: Thu Oct 23, 2014 8:38 pm Post subject:

5 inches of slack is mechanical.

As Wes said, use the manual and check everything. Begin at the front end.

I had nearly 90 degrees of play at the steering wheel with tires on the ground. I have replaced the tie rods, rebuilt the bellcrank and drag links, and am back to the steering box. The pittman arm has about 1/2" of vertical play at the box, so I am planning to rebuild the steering box next.

Once I get that done I'l check the the kingpins. I am fixing what I can see are obviously bad first and working my way down the list.

Brian
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Brian
1950 M38
MC11481
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album372&op=modload&name=gallery&file=index&include=view_album.php

jaycee · Member Joined: Feb 23, 2014 Posts: 19

one thing no one mentioned was bent wheels and hub flanges ive run into both. i would recommend you spin a bare known straight wheel on each hub in the front and then if all is well check your wheels. wheels not the tires. tires, thats a seperate issue but can cause similar problems. the death wobble gets set up by something not spinning true and then starts resonating with worn out bell crank bearings and rod ends etc. until the only thing to do is hit the brakes


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