Sudden onset of "death wobble"?

[JLeather]

Got the '67 out today for the first time in a few months. I've previously driven this truck over 80 mph, no issues. Everything from the wheels to the steering wheel is new (kingpins, tie rods, drag link, CPP box/rag joint, etc). The truck has always been twitchy in spite of adding some caster, but it's never done this before. Twice today at around 40-45 mph I hit a small bump in the road and sent the truck into a full on death wobble. Had to slow down to below 10-15 mph before it get under control. I didn't feel the wheel pulling much, the whole truck was shaking. What gives? All my reading on this says worn components, but everything's new and I haven't changed anything in the frontend since the last time I drove it (ok, a p/s pump, but no way that did it). Not really sure where to start here?

[PwrWgnDrvr]

Every time I have had that it was a bad tire on the front. Switch em to the rear and see if it happens again.

[Wildergarten]

Twice today at around 40-45 mph I hit a small bump in the road and sent the truck into a full on death wobble. Had to slow down to below 10-15 mph before it get under control.

is this a Dana 60 front end?

[martincom]

Check the rear, also. Loose lug nuts, broken springs/shackles, etc.

[Red383]

Every time I have had that it was a bad tire on the front. Switch em to the rear and see if it happens again.

I agree, it was bad tires on my 03 dodge when it happened to me. Scary *#%^ when it happens on interstate going 70mph.

[JLeather]

is this a Dana 60 front end?

Sorry, should clarify. D200 2wd longbed.

Every time I have had that it was a bad tire on the front. Switch em to the rear and see if it happens again.

I agree, it was bad tires on my 03 dodge when it happened to me. Scary *#%^ when it happens on interstate going 70mph.

The tires are pretty old. About the only thing I haven't replaced in the suspension over the last ~2 years. I'll have to check the date code, but they're probably 8 or 9 year old radials.

[Hobcobble]

Have you done any suspension modifications?
Does the CPP involve a non-stock drag link?

John

[JLeather]

Stock ride height, stock springs (a little saggy though, been meaning to replace them), CPP pitman arm is stock length. Draglink, tierod ends, and kingpins all stock and renewed within the last 1,000 miles or less. Relatively stock size wheels/tires (80's F250 16" rims and 245-75R16 tires). Tires are old, they were already on the rims when I got them on craigslist. Rear suspension is also stock, plus some old dealer-installed helpers (must be a total of 13 leaves). New cheapo Monroe shocks all around. No steering stabilizer (yet). Truck had one on it when I bought it, but I threw it away when I rebuilt the frontend. I figure it was someone else's bandaid for the worn out steering box.

I added ~4° of caster when I did the p/s conversion and I've been thinking of adding more because the truck is still a little twitchy for my taste. That and the scarebird conversion are the only changes to the frontend.

[JLeather]

One weird and probably unrelated question; are the front springs really different left vs. right? The truck has a slight lean to the right. Not a frame issue, you can see that the right spring is compressed farther than the left. I figured one just wore out faster and I've been meaning to replace them both anyway, but then someone on here bought a new set and they were marked "right" and "left". I wonder if I mixed mine up when I was redoing the frontend? Doubt that could have much effect on this issue, though the softer spring is on the right at the moment. Both springs have all the same length and number of leaves BTW.

[Wildergarten]

Stock ride height, stock springs (a little saggy though, been meaning to replace them)

OK, you've raised a possibility here, in that with the differences in spring rate between sides, they won't have the same fundamental frequency. Spring systems can develop resonances between standing wave frequencies. In this case, the system consists of both spring and tire, each of which has its own fundamentals. So if the impact was one that amplified said system resonant frequency, it could amplify, especially if the shocks were wimpy or worn. Try changing tire pressures and see if the speed at which this happens is any different.

[PwrWgnDrvr]

Start with the most obvious and likely cause - expired tires. They're unsafe as hell at that age, regardless! Especially at the speeds you are spinning them.
If you have driven it before, w/o issue, and it just started "suddenly", that would also indicate a tire problem, as they typically fail "suddenly". Springs and such wear out slowly and would be less likely to "suddenly" fail like you described. Especially since it happened twice, at different places, different speeds and different "bump" configurations.

[JLeather]

Put the truck up on the lift last night. Nothing obviously wrong with it; nothing broken or loose, shocks not leaking, etc. The tires are actually date-coded '02 it turns out, so I guess I'll start there...

[Series1Utiline]

If the U-bolts aren't tightened correctly, the spring locating (center) bolt ends up taking most of the side load and can break. This can cause the symptom you described.

[JLeather]

If the U-bolts aren't tightened correctly, the spring locating (center) bolt ends up taking most of the side load and can break. This can cause the symptom you described.

I'll take a look. I had to get taller center pins when I put the caster shims in. U-bolts were also new at the time and super heavy duty, but I'll make sure nothing is sliding around.

[JLeather]

New tires on. Bought a set of 215/85R16's. Took a few test laps and although the actual wobble is gone something still feels loose in the frontend. Especially on my gravel driveway I can hear/feel something rattling in the truck. I feel it in the floorboard, not the wheel. I thought it was a loose cab mount or something, but it's not. I guess I'll just start taking the frontend apart again from the wheels to the box and see what's loose or broken. I have also found that occasionally when static steering something in the frontend will "pop", especially when reversing steering direction. May be unrelated, but probably isn't...

[Hobcobble]

New tires on. Bought a set of 215/85R16's. Took a few test laps and although the actual wobble is gone something still feels loose in the frontend. Especially on my gravel driveway I can hear/feel something rattling in the truck. I feel it in the floorboard, not the wheel. I thought it was a loose cab mount or something, but it's not. I guess I'll just start taking the frontend apart again from the wheels to the box and see what's loose or broken. I have also found that occasionally when static steering something in the frontend will "pop", especially when reversing steering direction. May be unrelated, but probably isn't...

Did you replace the spring eye bushings?

John

[JLeather]

Did you replace the spring eye bushings?

John

I did, both ends. I did not replace the shackles or the bronze(?) bushings in the frame but they seemed to be a good fit still at the time.

[67LSD200]

First off, I really appreciate your documentation of what you're going through here. I finally grounded my 67 d200 after the death wobble became more of a half dead gallop! I had known from the onset that my kingpins were in dire need of replacement and upon disassembly it was quite obvious that the previous owner had done a replacement which likely rendered the contact area significantly worse than it possibly could have been from whatever actual mileage this truck has on it. Before the truck in essence became mobile merely by prayer and Mopar godliness, I had at one point found one of my u-volts to be flapping loose, after tightening that up it made a slight improvement, but progressively something was getting worse and maybe it was because I was so hyper focused on the front end that my senses were not being aware of other aspects, but, when the final left turn rendered the gallop that I previously described, in essence it felt like I was riding a horse and buggy with a wooden wheel cut by a drunken wheel Carver or whatever the people were called who made wooden Wheels LOL. The previous response that mentioned the resonance between variables of the leaf springs is one of the most insightful and eye-opening or mind expensive descriptions of the relativity between various components that at the end of the day all serve to make the tires roll properly as they should under various conditions and I should also add that, being that I I'm grossly under slept due to a forced move, my analysis of the physics behind what I found are certainly less valuable than the post I mentioned but, as I said before being hyper focused on the front end caused me to overlook until I hobbled the truck home over 25 miles at about 15 mph the fact that my u-joint connecting the drive shaft to the rear end head basically falling apart and was in fact operating solely by virtue of the sweptline gods that I all too often have relied upon.

[JLeather]

May have found an issue. Truck is back up on the lift. I pulled the springs back off and rechecked the eye bushings, all good there. I was putting it back together and greasing it when I found that my d/2 tierod end is loose. I can get more than 1/8" of squish out of it with a pair of channel-locks.
This was brand new maybe 500 miles ago (although it's been on there for a couple years). At the time I had to buy it from Rare Parts because it was the only place that had one in stock. Anyone got a source and/or a good p/n for a driver's side tierod end for a D200 with the 2800 lb axle? Should be the same as a D100?

[JLeather]

In answer to my own question, I'm gonna try an ES416L tie rod end. This is spec'd for 50's/60's Ford and IH half ton trucks and vans. It's the correct thread on the body (11/16-18 LH) and the same 1/2"-20 nut for the stud. Can't find specs on the taper, but as far as I know these things only come in a couple tapers. I've got a tie rod taper reamer if Dodge is weird. It seems the 140L tie rod end may be permanently discontinued.