I think I experienced "The Death Wobble" yesterday

[wilfreeman]

I've been putting some road miles on the ' a1 this week off. I have put about 40 miles on her since last thursday afternoon. Yesterday, after my last test drive, I made a couple of adjustments and put some air in the tires - 30 psi all around, which was up from 22 psi.

My Stepdad and his grandson showed up to pick up my daughter about the same time. They wanted to go for a ride, so we all loaded up (including my 6yo daughter) and took off. I had driven about 8 miles and turned down an old paved road. I got her up to cruising speed (about 35). About 1/2 mile down the road I hit a bump or depression in the road. Thats when the front tires started wobbling like the draglink or something had fallen off!

I slammed on brakes and pulled off into a side road and inspected everything I could get my hands on - everything was there and seemed to be tight! The tire did seem to turn easier though. I decided that she was safe enough to drive (slowly) home - about a mile.

I got home and pulled onto the concrete shop floor. After everybody unloaded I checked again. Everything seemed to be tight. I pulled on the top of the drivers side tire and it felt like the wheel bearings might be a little loose!

Needless to say, everything on the front end will be getting a twice over when I get off work next week! I'm not anxious to feel that again anyone soon!
_________________
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)

[oilleaker1]

Yep, front end shimmy. When you loaded more weight in it than usual, you changed the allignment up front, which helped set you up for the shimmy. It can be frustrating. Worn flat or opposite curved springs, out of balance tire, bent wheel, bad tie rods, loose or worn knuckle bearings, wheel bearings, loose draglink, bellcrank, sector shaft and worm gear, broken loose crossmember, toe in, allignment, all can be the cause. You just have to start at the loosest thing first and start tightening things up. Some guys add a steering stabiliser shock. I've found it might help a little, but you will still get the wobble. If everything is tight, look carefully at your allignment and spring/axle attitude setting. A friend of mine fixed his wobble by tipping the axle forward a little with aluminum wedges between the axle spring perch and spring. Allignment again!! You are not alone! John

[wilfreeman]

Thanks for the tips John! I was hoping it would be just a tighten a few things up and it's fixed type of thing, but it looks like it could be a bit more in depth than I figured. I have been really enjoying tooling up and down my stretch of the road (at 40 mph) this past week, and am ready to venture farther out on every trip.
_________________
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)

[Oldsalt]

Check out everything else, but overhaul the steering knuckle king pin bearings first. When they are set up correctly the front wheels are quite stiff to swing back and forth. Basically it can't shimmy when they are set correctly. You set the loading on those bearings by adjusting the shims under the king pin caps. You actually measure the stiffness when you are setting them up with a spring scale like a fish scale. 12 - 16 lbs to make the wheel start to pivot with the knuckle seals removed and the tie rod disconnected. Once the seal is installed it is even stiffer.

Check out this procedure on Novak's site for a really good description of the process.

http://www.novak-adapt.com/knowledge/steering_knuckle_repair.htm

[wilfreeman]

Yeah, I replaced the kingpin bearings - preload set, new seals. It felt like loose wheel bearings when I shook the top of the wheel - anyway, I will be tearing into on my next day off. The box, bellcrank and draglink have been rebuilt. The tierod ends are new. It could be anything that I rebuilt needing adjusting (thats the reason for test driving, right).

Also, I aligned the front end with a tape measure to get it close - hasn't been professionally done, and the tires are new, but they didn't balance them.

As you can tell, I have a lot of possibilities here. I will start with checking everything for proper adjustment. Then, I can move on to taking it to a shop for balancing and alignment.

Would inflating the tires to 30 psi affect it? I read somewhere that one of the fixes for an m211 with the death wobble was to lower the tire pressure. I had just adjusted the tire pressure from 25 to 30 psi before this test drive.
_________________
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)

[artificer]

Don't go jumping from pillar to post on this....you asked did/would tyre pressure affect this & the answer is yes but there is something else that has been influenced by increasing type pressure so letting them down is not the fix. Also someone indicated wedges that tilted the axle forward...it is actually backward but should not be needed if everything is right. The only alignment that can be altered is toe-in.

Firstly with all wheels on the ground how much steering wheel movemnt is there before the free travel is gone? Have someone rock the steering wheel & see if you can identify any movement in any of the steering linkages & steering box?

Secondly jack one front wheel @ a time....grab the wheel top & bottom Then rock in & out.
Everything fine there should be no movement.
If there is movement have someone apply the brakes.
This action, if it eliminates/reduces movement, indicates the wheel bearings need service/adjustment.
Movement still there or reduced means the king pin bearings need service/adjustment.

This whole exercise should take about 10 minutes & you should then know what you need to do.
_________________
John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND

[wilfreeman]

Thanks John! I'll print this post out before I lose it - I won't have time to check until I get off work next week. I'm pretty sure there is a couple of inches of movement before the wheels move - draglink suspected. It seems like I looked at that before.

Now that I think about it, I might just sacrifice a little sleep tomorrow anyway. I just know that once I start, I won't be able to pull myself away from it until it's fixed or I at least know what the problem is for sure and come up with a plan to fix it. I guess thats part of the green disease!
_________________
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)

[wilfreeman]

Alright, I finally got around to working on her. So far I've found 4 things wrong in the front end. 1)The driver side wheel bearings were loose, 2)Bellcrank was/is loose, 3)Drag link is jacked up and 4)Sector shaft bushing is worn out.

- I re-adjusted the wheel bearings.
- I tightened the clinch bolt(?) on the back side of the bellcrank which took alot of the play out out, but not all of it - I was kind of scared to torque it down too much more.
- I tightened down the drag link plugs, but won't know if that helped any until I fix the sector shaft bushing.
- I lowered the tire pressure back down to 25psi.

On the test drive (about 6.5 miles) I didn't experience any wobble, and it was slightly tighter (because of the wheel bearings).

I will be getting the tires balanced on Wednesday, but the bushing won't get replaced until after the rally in October.
_________________
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)

[pockers]

I occasionally get the wheel wobble when i hit a decent pot hole or a speed hump too quick
To fix i have to break to a near stop but this is only a temp fix

Glad to have found this topic and will endevour to properly cure the problem on my a1 here in the uk

[wilfreeman]

Yeah, it is a scary feeling! I talked to a local guy today that owns an M38a1 and he says when his does it, he knows his tires are not inflated right! He also said that his steering gear needs rebuilding too.
_________________
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)

[wilfreeman]

A little bit of an update on my steering issues - A YEAR LATER!

I rebuilt my spare steering gear after the Georgia rally last October. I installed new bushings, bearings, seals and set the preload correctly. That took a bunch of the play in the steering out, so I left it there.

I took it to the NC Steel Soldiers rally in Denton, NC in April. My main issue there was it wasn't running good - in addition to not steering great.

I took her out for a short drive last week and hit a pothole at about 35mph and she started the death wobble! I tried jabbing the brakes and a quick jerk on the steering wheel. I ended up having to pull off the road to stop it. I had to find the problem before I took her to the rally IN A WEEK AND A HALF! Luckily, I had ordered a bellcrank rebuild kit last year, but never got around to installing it.

My bellcrank had about 3/8" of up and down movement at the ball end. I pulled the bellcrank off and put the rebuild kit in it. The new bushing to bearing fit was looser than the original setup. I cleaned the cinch bolt slot out because it was completely filled with grease and dirt. I polished the inside of the frame casting. I put everything back together and greased it up. I ended up with maybe an 1/8" of up and down movement on the ball end of the bellcrank - a major improvement in my book!

When I reinstalled the draglink, I put a little more torque on the big screwdriver I was using to tighten the plugs with a wrench (I do not have the correct drag link plug socket). I was able to crank it down a lot farther than I did the last time I worked on the steering. I went to tighten the pitman arm end and realized I couldn't get the screwdriver in there and crank down on it - that got me thinking! I looked around the shop for a little while until I found a piece of flat bar that measured 1/8"x3/4"x2"long - it fit the drag link plug perfectly. I tried to turn it with vice grips - no go. Tried pliers - no go. I finally settled on a 12pt 11/16", 1/2 drive socket and ratchet - perfect fit! I was able to crank the plugs down until completely seated and back them back out per spec.

I checked the tire pressures and adjusted them. I tightened up all of the spring shackles.

I ended up with maybe an inch of play in the steering wheel! This is way down from the 3-4" I had previously! I had to jump in and go for a ride. She drove like a new one! I hit all of the potholes I saw on purpose just to see if I could get a shimmy - and I didn't! She is actually a pleasure to drive now ( I rebuilt my spare carb and installed it and put some ethanol free gas in her - purrs like a kitten!).

I'll be off to the rally next week for some trail rides and the 45 mile (round trip) hardball convoy to the bbq joint like last year (I drove her about 55 miles on trails and 45 on the convoy last year in the 4 days I was there).
_________________
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]

Nice days work followed by a pleasant drive.
_________________
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

[wilfreeman]

Got that right! I put right at 30 miles on her that day.
_________________
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)