1987 4x4 death wobble - type vibration help

[DeadStang]

Back story: I have my dad's 1987 pickup as my daily driver. It sat for a bunch of years after he passed, then I finally inherited it when the step mother couldn't move it as the clutch M/C dried out. Fast forward 2 years and many thousands of dollars at the shop in deferred maintenance, etc. later. It has 114k miles and was lightly used in his life. I have a set of TA radials that are a couple of years old with only a couple of thousand miles on them (may not be relevant).

Issue: At around 40mph and 60mph, it has a fairly noticeable vibration. I also drive Jeeps, which are somewhat notorious for having a "death wobble" when they've been lifted or have worn front-end components -- this is not as bad as the videos of Jeep wobbles, but it's pretty significant, although I don't feel like I'm going to wreck the truck.

So I took it (back) to the shop and bitched about about it and they are convinced it's just a tire issue as they say nothing is worn in the front end and it passes all 800 or so of the check points they look at. This is a good local shop, not just a gas station mechanic. So I took (back) it to the tire shop who sold me the tires and had the tires re-balanced (yes, a wheel/tire or two needed tweaking). The shop made the mistake of calling me to see how the truck is running (they replaced a head gasket after breaking all the exhaust bolts trying to fix a pretty nasty exhaust leak) so I bitched about the wobble (again) and they want it back (again).

My question: Guesses on common causes of vibrations on a relatively low-mile truck? Surely the shop is looking at obvious stuff like a u-joint and have already ruled that out. Allegedly all the front-end components are fine...but the truck is obviously not fine. The vibration isn't bad enough that I need to slow down and am not scared driving it, but if my teenage daughter notices the vibration, it's not just a princess and the pea sort of thing. Could the tire shop be such bozos that literally they balanced them wrong when I bought the tires and were unable to correct that the second time around? Could a flat spot in a tire make the truck vibrate that much -- and wouldn't the tire shop notice that when they took them off a month ago?

[LugNut1990]

Try swapping the front and rear tires. Vibration change or go away?


Also need to check everything else underneath, including, for example, the engine and transmission mounts, frame, crossmembers (and their bolts' torques), control arm bushings, etc.

[alabama_lowlife]

Start by looking over everything yourself if you can. Check the driveshaft carrier bearing to see if it has dry rotted and deteriorated. Have someone move the steering wheel while you observe the steering parts for play. Wiggle the tire to try to find play in the wheel bearings and ball joints. If nothing jumps out to you try taking it to a new shop. And get the tires check by a different shop as well

[VOTS95]

Make sure your driveshaft is in phase per the following pic. If it's wrong, you'll get some vibration from it.



VOTS

[dvdswan]

It sat for 2 years, was that in a field? driveway? any chance that dirt/crud/mud settled on the rims on the inside of the wheel? If not cleaned off this will cause an out of balance condition.

Have the front wheel bearings been repacked?

Do you feel this vibration in the seat or in the steering wheel?

[Reserector]

Is it lifted? In other words, are the lower control arms level (ish) as you look at it from the front, or are they angled downward toward the tires? Too much angle will amplify the slightest bit of play, causing death wobble in IFS.

Has anyone rotated the front tires to the rear? An internally delaminating tire will balance fine, but have a weak place that will make it bounce, for lack of a better description. Diagnose this by rotating the potential "problem tire" to the rear.

[89'HBV6]

Welcome to IN...

There are some really good suggestions here. Please let us know what you discover...

[cadillacdude1975]

It is 35 years old. My guess is it needs every bushing and steering component replaced.

[89'HBV6]

Originally Posted by cadillacdude1975

It is 35 years old. My guess is it needs every bushing and steering component replaced.

Yes, I concur with this. With this it's NOT the mileage, it's the age of the parts... and some are rubber.
You'll be happy once done and it fixes your problem.

[XoXSciFiGuy]

Yeah...I would be looking at the carrier bearing especially. It is also important to determine WHERE you are feeling the vibration. If it is mostly in the steering wheel...then look to your front wheels and front suspension components.

If it is mostly a CAB vibration, then look farther back to the u joints or carrier bearing.

Also...like someone else said back there...if someone pulls the rear driveline from the tranny to pull the tranny out for a new clutch...and they don't MATCHMARK the driveline and the tail of the transmission...and just stick that driveline back in there NOT the same spot...this will cause vibration. When you see those little weights welded to a driveline, there is a reason they do that. Driveline must always go back in same spline spot it came out.