dangerous shimmy at 35-40 mph

Sal · Post by **Sal** » Sun Aug 31, 2008 6:26 am

For some reason, a couple weeks back, my M38 developed a scary shimmy at speeds above 35. it is so bad, i no longer drive it. So far, i have replaced the wheel bearings(they wre bad), verifed that the tire balance is correct, no bent rims, tie rods ends are fine, no slop or play in the drag link, bell crank and the bolts are new. Regreased all joints. Front end alignment is right at the 3/16" toe-in spec. I'm pulling out the last few hairs that i have. What have i missed? I completed the restoration on her 3 years ago and have driven it all over with a hint of this. Any help is greatly appreciated. Thanks.

Hotlips · Post by **Hotlips** » Sun Aug 31, 2008 8:52 am

Hi Sal - I had exactly the same problem on my 1943 Willys jeep some years ago and it was caused by a loose steering peg in the steering box. I don't know what sort of box the M38 has, but it is worth checking the steerinf box out anyway. Good luck - David (mujibee)

Post by **wesk** » Sun Aug 31, 2008 8:53 am

Check the steering pivot bearings often referred to as the king pins. Raise each front wheel off the ground and grasp the top and bottom of the tire and rock the top in towards engine and out towards you. More than a 1/8" to 1/4" of movement at the top edge of tire means they are worn or loose. If they check good then trade the front tires with the rear and test drive it.

Sal · Post by **Sal** » Mon Sep 01, 2008 3:42 pm

Thanks folks-- i've rotated the tires as Wes suggested and it did get a lot better--still did it above 35 but not every time. i checked the steering box adjustment and found it to be to tight. Readjusted it to the book recommendation and i now have a slight shimmy at low speeds over a washboard type road but it quickly goes away. The king pins are in great shape. I have now noticed that the bearing in the steering column does not allow the steering wheel to rotate smoothly--kind of stiff and than loose--i'm thinking it's bad and can lead to the shimmy i am experiencing. Thoughts?

Wes--thanks for the advice, i thought for sure the tire rotation did the trick but it came back after about 3 miles of driving.

Post by **wesk** » Mon Sep 01, 2008 6:19 pm

The steering gear box lash adjustment must be done with wheels centered due to the design of the Ross gear box. If not the steering will bind as you move away from the straight ahead position. The top and bottom worm bearings have a design preload and are adjusted by the use of shims. All of this info is in the TM 9-1804B pages 159 and 160.

SteveJ · Post by **SteveJ** » Tue Sep 02, 2008 4:28 pm

I had a similar problem with my M38 I checked all the componants and the problem turned out to be the steering bellcrank. I installed a new bearing kit and have not had a problem with it since.