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I took my M38A1 to Long Island, NY for the week (about 2 hours from my house). Trip and first few days were no problem. Just yesterday, when I hit about 40, it started to shake side to side. It wasn't pulling to the right of left, just shaking pretty hard. That continued for a few minutes, I hit 45, and it went away. I slowed a little later, and right around the same speed it did it again. I checked tire pressure, and inflated them to 35 (from a little under 25). I checked the rims , and two of the lug nuts on the rear passenger side were loose, I tightened them. I took it for a spin, and right around the same speed if happened again. The wheel and kingpin bearings are new, as are the tie rod ends. Anybody have any clue what's going on?

Sounds like "death wobble" for Dead Guy! I've been here. It can be caused by a bunch of things: Tire balance, bent wheels, loose knuckle bearings with a worn spot in the races, loose sector shaft in the steering box, including side shift of the sector, worn bell crank, worn tie rod ends, bad caster/camber, springs gone too flat changing the alignment, loose wheel bearings, anything that controls the alignment and steadiness of your two front wheels. Even the tires themselves. Once the two tires get a off balance gyro effect, the wobble begins. You have to slam on the brakes and slow to get the gyro wobble thing stopped. Mine have been caused mainly by looseness somewhere and tires not well balanced or poor quality. On my Jeep pickup, the four bolts holding the pittman arm to the bottom of the knuckle were loose. my CJ2A had worn knuckle bearings and races. Another was bad tires. You just have to investigate all possibilities. John

Yes, all of the above. You mentioned that the king pin bearings were replaced - did you set the proper pre-load on them? Once that is set and with new knuckle seals the knuckles become quite stiff and have a good amount of resistance to turning. That resistance, plus little or no give due to worn or loose parts elsewhere in the steering system, reduces the chance for death wobble.

Well, here's the weird thing. I had a horrible death wobble before I rebuilt it. I put in a new bell crank, new tie rod ends, new kingpin and wheel bearings, a whole new steering column and box, and a steering stabilizer. The wobble went away for quite awhile, and many long trips. Just recently, it started at over 40 mph, and I found out the front driver rim was bent. I swapped it with my spare, and all was good. Then I made this long trip out to NY, and it seams to have started again.

The "Death Wobble" has been around to plague all owners of old closed knuckle 4WD's for over 60 years. The causes are the same and haven't changed. Suggesting that since all new parts were just installed does not mean you have found a new cause for this problem. It means one of your new parts was: installed incorrectly, adjusted incorrectly, was not a very good new part, or has already worn out or failed.

Every possible cause for your symptom was listed above. Have a trained suspension mechanic, preferably with a few gray hairs review the above list while inspecting your jeep's equipment.

Isn't this the same jeep you said in an earlier post is never driven long distances?

Rarely driven long distances. I used to live on Long Island, and I had a bunch of people dying to see it. I can count on one hand the times I've taken it on over 45 minute trips.

When I've experienced death wobble, it hasn't gone away until the vehicle came to a complete stop, or close to it. I've never had it go away by speeding up. Plus wouldn't having a steering stablizer keep the wobble away, even with worn parts?

Over the last 44 years I have driven jeeps with the death wobble that will go away by changing speed either up or down and I have driven them that will only get worse up and only quit by slowing to 5 or 10 MPH and applying the breaks.

In every case one of the previous listed conditions was the cause.

My old M-37CDN used to get a death wobble occasionally, usually a quick turn to one side or the other straightened it out. A new idler arm bushing cured it permanently. One thing to watch for on older vehicles is an out of round front brake drum. A few years back, I was traveling on a logging road I had not been on before, and had a hill kind of sneak up on me. I had to use the brakes a bit to snub her back, and as I came around the corner at the bottom of the hill, I noticed a huge puddle. No time to avoid the whole puddle, and my driver's side steering tire went through it. WELL, the cold water INSTANTLY warped that brake drum, to the point the truck was un-driveable. Even after loosening off the shoes, it still wobbled and shimmied at any speed over about 25MPH. Something to keep in mind.

So, even stranger. A car parked behind me, and I had to dramatically turn it to the left and right to wiggle out of the spot. No more wobble at any speed. And I drove it home from Long Island to Philadelphia last night, a 2 hour trip.