CUCV M1008 wobbling. Help needed

[MattTurbo]

Hi guys, I'm finalizing the purchase of a '85 M1008 in Germany.
Everything looks fine: no rust, no oil leaking, suspensions are good, frame is good. It starts immediately and engine runs smooth without rattling noises. 65k miles.
Modifications: new type of water/fuel filter separator, new hoses, new alternator, new belts, glow plugs are bypassed, doghead relay mod.
Very minor defects: 2 small dents on the body, triangular windows need new gaskets, voltmeter is not connected, color is odd (I can repaint it) and the pump for washing the windshield doesn't work.
Major defect: it has a ruined tired with a bubble but the owner will buy a new set of tires. Toe-in must be adjusted because vehicle goes on the right while driving on straight.
My main concern is the wobbling while driving, especially at low speed. In my opinion (I'm not a mechanic) it comes from the front part.
It's like one of the tires has something under it or it's oval or you're always running over a small obstacle. If you increase the speed the problem is less obvious.

Could this be the damaged tire or a major problem on the transmission? The shafts under the frame look straight. Nothing is moving if shaken by hand. All joints are well greased.
There are no dents on the brakes or rims.
I've attached some pics of the bubble.
I'm asking your help because the M1008 is 500miles from home and I would hear some expert opinions.

Thanks!

 

[NDT]

Sounds like what is called “death wobble”, can be caused by many issues but by far the simplest to fix is tire defects like you have. If problem remains after new tires, the knuckles on the front axle will need overhaul.

 

[cucvrus]

I have encountered this on a few trucks I owned over the years. My experience has been that once you have a truck that has the issue it is fairly easy to repair. he cost is relatively less than $300. First thing is to eliminate that the tires are not causing the issue. Many times if I had a truck that didn't ever get the wobble I could not make it wobble with square tires on it. Other trucks new tires fresh alignment and the wobble would come as soon as a bump in the road or a bridge joint was hit. Scary at 65 MPH and it won't go away until you are almost stop. And it may come back right away. I found several underlaying issues that contribute to the wobble.
1.) This is the out front axle U joints being tight and in some cases seized. I had them that tight on M1009 and M1028/M1008 that they would pop when they finally decided to turn. I had a 1984 M1008 that would crack under the cab when I went around a turn and you would fight to get it back straight. The crack was the cab mounts on the rea of the cab. On the 1984 models they were just a perch on each frame rail and had a thin piece of angle connecting them. It was so tight it sheared the 5/16 bolts that attached it to the frame mounts. Really. See it. It was a low mileage CUCV and it was still 10 years old. I changed the outer U joints and that fixed that one.
2.) others I repaired had worn out tie rod ends and drag link. That was easy. Replaced them with new and had a real alignment done and no more issues. Keeping the new joints greased and maintained was important. I see the bone dry vehicles that people grease and the grease never gets past the grease fitting. It is packed solid inside with rust. And the grease that does come out is like valve grinding compound from all the rust and metal particles that are suspended in the grease and wearing the joint out smoothly. Sort of like toothpaste and hand cleaner with pumice. Get the point?
3.) Big GOOFY non stock out of balance tires and wheels. Obviously you know the reason there. Will it go round in circles?
4.) On the M1008/M1028 and other 1 ton CUCV variants I have serviced the front brakes and the slides of the knuckle so that the caliper can return to the neutral position after the front brake pressure is released. I removed the calipers and sanded the slide surfaces on the caliper till smooth and the surface on knuckle. I greased that area and replaced the slide wedge and tightener piece. Again may not be the proper terminology but you get the point.
5.) after repairing the issue it is recommended that you maintain the parts with good quality grease and live happily ever after. Till the next thing arises. Vehicles have changed. We have a 2015 GMC 2500 with 267K miles on it and it just keeps going. I the beginning when we bought it brand new I had my doubts. The front driveshaft broke off and punched a home in the floor during a big snow storm. But I never encountered any of the issues I continue to have with CUCV's and older trucks. IMHO things have improved greatly in the past 35 years. Good Luck. I hope this is helpful. If it were mine I would check everything I listed and save the coin of changing the steering linkage after all else fails. Report back. I am anxious to know the issue. You may have something I have never seen after all these years of wrenching.

 

[cucvrus]

As a final recommendation I would double check the steering box and make sure the frame is not cracked and the bolts on the steering box are tight. I only ever had 1 broken frame and that was on an M1009 with a snow plow and bound up front axle U joints. I used the Off Road Design weld on frame repair kit to fix it and a rebuilt steering box with new rag joint and have not had issues since. Good Luck.

 

[MattTurbo]

I have encountered this on a few trucks I owned over the years.....

Thank you for your reply.
I will try to have the truck inspected in Germany before paying it. It's not the easiest way 'cause I live in Italy but I can manage this.

 

[MattTurbo]

Sounds like what is called “death wobble”, can be caused by many issues but by far the simplest to fix is tire defects like you have. If problem remains after new tires, the knuckles on the front axle will need overhaul.

Are this the knuckles I should replace?
I'm not English native and some technical terms are difficult to translate.

 

[NDT]

Are this the knuckles I should replace?
I'm not English native and some technical terms are difficult to translate.

No not the entire knucke! There are plastic bearings that need to be replaced. Off Road Design is a good parts source for upgrade design parts. The oem parts are flimsy.

 

[cucvrus]

GMC Ford Dodge Chevy Dana 60 70 Alignment Kingpin | McBay Performance
I spoke with a freind about this years ago and he said that the wobble was not caused by caster camber adjustment but toe in and out. And also loose steering linkage. He is the man that gave me the insight to the issue and I added a few other causes to the wobble issue over the years. He has passed and I miss him and his years of knowledge. I looked back at my notes when I got home. Another thing I failed to mention was the simplest of all. The steering damper. 1984 Chevrolet K30 Steering Damper - KYB SS10325 (stockwiseauto.com)
Keep in mind that would be the easiest fix of all and it has been the culprit on a few I worked on over the years. If it has no resistance when you remove it or appears wet it is NOT doing the job it was designed to do. Not sure how I forgot to mention that but I did and wanted to set the record straight. The parts I listed up top were added on a friends K30 wrecker to improve tire wear. GMC Ford Dodge Chevy Dana 60 70 Alignment Kingpin | McBay Performance
Good Luck. None of these issues would stop me from buying the CUCV. Unless it has been horribly cobbled together and has signs of frame damage. Everything can be fixed.

 

[Curtisje]

I had the death wobble on my m1028. It was out of alignment... toe in. Once I got it properly aligned the wobble went away. 25,000 miles ago.

 

[Keith_J]

I had death wobble in my M1031 with less than 10,000 miles on the odometer. Replacing the upper king pin bushings and springs helped greatly. The right front tire had a belt failure a few thousand miles later. New 16x8 rims with 255 85 16s positively ended the problem.

 

[royalflush55]

A new Heavy Duty steering damper will fix a lot of death wobble issues. If these are original they are usually shot.

 

[nyoffroad]

A new Heavy Duty steering damper will fix a lot of death wobble issues. If these are original they are usually shot.

No, it hides the problem until the problem (lets say loose tie rod ends) are so bad that it not only becomes a safety issue but also causes your shimmy shock and other parts to wear out. Do it once and do it right.

 

[royalflush55]

Ok, if your tie rod ends are loose replace them and then put on a HD steering damper to prevent tie rods from wearing out prematurely!