Violent Fron End Shaking
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From: Suffolk, VA USA
Violent Fron End Shaking
Guys....gotta a head scratcher here.
86 F-150 4x4 w/4 inch lift and 32s. The truck drives just fine the overwhelming majority of the time. No excessive play in the wheel. Tires are wearing just fine. But every now and then, when I hit a moderate bump at between 40-50 mph, the truck develops an extremely violent front end shake. I'm talking 9.0 magnitude earthquake-like shake to the point that the truck is completely out of control. After about 20 mph of speed comes off the shake will go away, and may not re-appear for weeks. I've been through everything I can think of and can't find anything wrong. The ball joints, bushings, steering linkages, axle pivots, radius arms, shocks, springs, front axles, hubs, and all the mounting points check out fine. I've gotten under there with the front end on jackstands with a large pry bar and can't find any play in anything.
I'm stumped. Anybody out there ever deal with something like this?
Thanks
86 F-150 4x4 w/4 inch lift and 32s. The truck drives just fine the overwhelming majority of the time. No excessive play in the wheel. Tires are wearing just fine. But every now and then, when I hit a moderate bump at between 40-50 mph, the truck develops an extremely violent front end shake. I'm talking 9.0 magnitude earthquake-like shake to the point that the truck is completely out of control. After about 20 mph of speed comes off the shake will go away, and may not re-appear for weeks. I've been through everything I can think of and can't find anything wrong. The ball joints, bushings, steering linkages, axle pivots, radius arms, shocks, springs, front axles, hubs, and all the mounting points check out fine. I've gotten under there with the front end on jackstands with a large pry bar and can't find any play in anything.
I'm stumped. Anybody out there ever deal with something like this?
Thanks
Logistics Pro
Joined: Jun 2008
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From: Florida
Oh wow man, death wobble is serious stuff. Hard as heck to diagnose too.
Have you checked the mounting bolts for the steering box? Are there any cracks in the frame? How about your radius arm and pivot arm brackets?
Have you checked the mounting bolts for the steering box? Are there any cracks in the frame? How about your radius arm and pivot arm brackets?
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From: Suffolk, VA USA
Steering box bolts and mounts are fine...bolts are torqued to spec. I haven't pulled the box to check behind it yet, but no visible cracks on the frame. Axle pivots and radius arm brackets are solid. The pivot and radius bushings are poly with less than 30K miles on them. No play in them.
Logistics Pro
Joined: Jun 2008
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From: Florida
Hmm, reason I mention this is because it was a problem on some of the dentsides, and although I haven't heard much about it on our generation, it is still entirely possible. If I recall correctly, the cracks were behind the steering box. :/
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From: Northeast, OK
You probably won't see a belt problem. If one breaks loose it will cause the tire to not be able to be properly balanced.
However, what you are describing doesn't sound like belt as that doesn't usually cause that kind or severity of wobble. As Shaun says, that sounds like a death wobble. From what I know of those it is usually a combination of bad or worn parts, not any one in particular.
The lift and the 32's aggravate the situation. Do you have other tires you could put on for testing?
However, what you are describing doesn't sound like belt as that doesn't usually cause that kind or severity of wobble. As Shaun says, that sounds like a death wobble. From what I know of those it is usually a combination of bad or worn parts, not any one in particular.
The lift and the 32's aggravate the situation. Do you have other tires you could put on for testing?
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From: Virginia
How did you check the shocks? I had this one time, and accidently found the the bracket that mounted the shock was loose. I just happen to knock against it and it wiggled a little bit. Fixed that and my death wobble went away. It's going to be something loose, unless you hit something hard recently and knocked it out of alignment.
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From: Suffolk, VA USA
Thanks guys....I don't have a spare set of wheels, but I will roll the fronts to the rear....if its a tire that should move the problem to the rear axle. The shockas are actually brand new. I keyed on them early and found one that acted like it might be sticking a little, so I just replaced all four. Everything mounted tightly with all new hardware and poly bushings. Until today I thought that had fixed the problem.
I'll get it back up on the stands over the next day or so and re-check everything. Didn't find anything loose the first time around, but it won't hurt to double check everything. If that doesn't work I'll start disassembling looking for hidden cracks or other problems....
I'll get it back up on the stands over the next day or so and re-check everything. Didn't find anything loose the first time around, but it won't hurt to double check everything. If that doesn't work I'll start disassembling looking for hidden cracks or other problems....
This space for rent...
Joined: Apr 2009
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From: In the garage
Bill, I've been dealing with the same issue for a month now on my '84 (4" lift and 35's). It doesn't happen all the time (35-45 mph, moderate bumps as well), but my truck sees little actual road time, so it makes it a PITA to diagnose. Checked every nut and bolt, all hardware is new on the front end... pretty much chasing my tail right now. Obviously I'm no help at this point, but I understand your frustration. If I find the culprit on my truck, I'll let you know.
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From: Suffolk, VA USA
I've read death wobble is most common on trucks with coil springs, solid axles, and track bars. But judging by all the literature out there it can happen with just about any setup. My truck has the TTB with coils with no track bar.
Logistics Pro
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From: Florida
Most of the vehicles I've seen with death wobble are Jeeps. 4x4 and 4x2. Both have a straight axle type deal in the front, the 4x2's are just missing the differential section. Don't know why it ends up that way for me. Neighbor's Jeep has a bad case of it as we speak. She can barely keep control of it.
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Well, found it. Of course its nothing simple like a bad ball joint. The crossmember is cracked basically from where it meets the frame right behind the steering box, running up on the inner crossmember to a rivet near the top. Of course, its doubled up on the outer crossmember and that part's not cracked, so the only way to get at this is from the inner crossmember. I'm not sure if it can be welded without pulling the whole front pumpkin out, if it can be welded at all. My brother-in-law is a shipyard welder, so I'll get him to take a look at it. Then again, I haven't done a chasis swap in a while....