My truck is a 1979 F150 with 6" suspension lift and 3" body lift.

Recently I moved up to 39.5x15-15 super swampers, on 15x10 wheels with about 3 inches backspacing. Before I was running 305-85/16 buckshot mudders, which measured about 35x12, on 16 inch wheels with almost 0 offset.

Everything was fine until I put these tires on. I used equal balancing compound when the tires got mounted.

Ever since I put these tires on, when I get up to about 25-30 mph on pavement, the steering wheel will start moving side to side slightly in my hand. If I hold the speed, or accelerate it gets worse slowly at first then very quickly, until the whole front end is shaking violently, and I can't even steer anymore. At this point I hit the brakes, and it gets worse while I am slowing down, until about 5 mph, when it finally stops. It has shaken hard enough to break all my grill mounts.

So far I have done the following:
New steering stabilizer
New track bar bushings (Poly)
Alignment


My tie rod ends were replaced this summer, as was my draglink.

I have a brand new steering box.

4" drop pitman arm

I am running 7 degree C bushings with custom 4" dropped radius brackets.

Has new radius arm bushings

Tires show no bulges, have about 85-90% tread, no cupping

I have checked the ball joints, and so has the shop that aligned it, and they are all tight.

I am pretty baffled at this point. I know I have a little too mush caster correction for my 6" lift coils, but that is because I planned on going to 9" coils soon. Everyuthing seems tight. The only things I can think of doing would be to put new shocks on the front, possibly a dual shock setup, and maybe add another steering stabiliser.

If anyone has any ideas it would be GREATLY appreciated. Been a pretty frustrating problem.

Thanks!

Dan

 

Correction: I have 4 degree C baushings with the drop radius arm brackets.

 

I have had the same problem. First try swapping out the tires with a different set to eliminate the tires. Next, check your wheel bearings. I took out my hubs and found one bearing had backed out! Yikes! I tightened it up and it seemed to do the trick. I get the shakes when i hit a small bump in the road. It starts small then gets violent. I have to slow down or swerve to get it to stop. Forty bucks or so for new bearings and races and you should be set. Let me know if that does the trick.

 

Thanks, I will try that when I get a chance to work on my rig, prolly sometime later this week or early next week.

Dan

 

All big tires are like that, it comes with the territory. You can check for roundness. Set a straight edge on a cupple of blocks in front of the tire and spin the tire by hand to see how it comes and goes against the straight edge. My guess is its going to look pretty bad. You can exchange them, Super Swamper is usualy pretty good about that. If its not too bad you can have them trued, but it voids any warrenty.

 

I really doubt that the tires by themselves are the cause. I think I would still at least be able to drive it. I am in a 4 wheeling club up here, and lot of the guys are running 44s, and they can still drive down the highway at 50mph no problem. I can't even drive 25. Thier trucks shake and shimmy a great deal at certain speeds, but it is NOTHING compared to what my truck does. And most of them didn't even have thier tires balanced like I did. If I were to dry to continue driving it once it starts doing its thing, I am almost certain the front axle would leave my truck, thats how hard it shakes. And its not like a wobble, its a little like a shimmy, but not quite. Each side of the front end starts taking turns jumping up, until its so bad you are bouncing in the cab, can barely hold onto the steering wheel, and can't steer at all, and you getting pounded around so hard that its hard to even hit the brakes to slow down. I am amazed I haven't yet broke anything else besides my grill mounts.

I had a guy mount them up on his bronco and they went down the road great with just a very minimal shake at about 40 mph, dissappears at 50.

I have since checked the frame for cracks, took the steering box off and checked behind it for cracks, and made absolutely sure all the bolts are tight from the steering box and track bar bracket on down.

I did find a bolt missing on the lower coil "pad"... I dont think this could cause any problem though.

I have one question too, if anyone knows for sure: Can excess castor angle cause this problem?

Dan

 

Sounds like " death wobble" do a search on it. If you still have questions the guys in the 4x4 forum can help you, they know this problem well.

 

First, don't worry about too much poss. caster,negative caster is what you don't want.Second,balancing compounds are a "crap-shoot" when it works it's great,but I have seen more problems with it than success.Check tires for any "run-out" either up/down or side/side, that tire has alot of sidewall and at speed it can get the momentem going, any loos-ness in trac-bar will be multiplied,don't remember if you had a steering damper but would be worth it.Check for shop that can do "on car" balancing in your area,at my shop we automatically balance anything over a 36" on the vehicle, like to say "Do it right or Do it twice".Good luck

 

If you're asking what "Death Wobble" or DW is all about, it is a situation where the front axle begins oscillating with such violence that control of the vehicle is difficult until slowed down, and the entire vehicle shakes to the point you feel it will come apart. Although I have heard much discussion, DW apparently isn't caused by any one factor, but may happen if any of the following are present (not necessarily in this order, either):

• Loose or worn Trackbar mount. The trackbar prevents (or reduces) side-to-side motion from the four-link front suspension on the XJ, MJ, TJ and ZJ Jeeps. If the ball joint is worn or the trackbar mount is loose, it can allow lateral wobble as described above
• Poor alignment. The front tires will be toed-in following the lift; when you hit a bump on only one side of the axle the tire will begin to bob up and down. Since the Control Arms are no longer horizontal, they will pull that side of the axle farther back as it goes down - this will turn the wheels slightly to that side. Once the tires pull to that side, the 'scuff' of the vehicle traveling straight ahead will slow the tire and begin the same process once again. Drop Brackets can also help reduce this, since they bring the control arms back to a more horizontal position. Sometimes this can be caused by excessive toe-in of the front wheels-think of it as the tires being cross-eyed and not knowing which tire is dominant
• Poor Alignment (Part II). Lifting the Jeep involves changing the caster of the axle. If the stock control arms are used, the pinion will start pointing down, away from the t-case output shaft. As it points down, it changes the caster of the axle and therefore throws off the self-centering engineered into the axle. Remedy this by using adjustable control arms.
• Unbalanced tires. Once again, as they start throwing the axle around, the only way to stop it is going to be by slowing down.
• Steering Stabilizer. A tight steering stabilizer can mask problems with the steering, but if it's loose it may allow DW to occur in cases where it normally wouldn't have.
• Ball joints. Worn ball joints are a danger anyway as they may fail and cause uncontrollable steering loss, but by allowing the wheel to move laterally and independently of the opposite wheel they can also contribute to DW.

 

thanks guys, I have a lot more stuff I can check now. I really think I'll be able to nail it down. I will keep y'all posted.

Dan

 

I got a chance to work on my rig today. I found that the tie rod ends are shot, both of them. I originally ruled them out because I replaced them 5 months ago. I have only put 3000 mi on the truck since then, and they were greased a bunch of times over that period. Out of that 3000 mi, very few were off road because I haven't had time. The vast majority of those miles were on the highway. '

I put in a new post about what to to about my tie rod ends in this section of the forum, if any of you guys have suggestions as to why they wore out so quick or what I can do to "upgrade" my tie rod ends please reply there.

Thanks again for all your help

I am waiting for some input before I buy new tie rod ends, and hopefully that will cure the DW.