Thanks for the ideas everyone. I'll look into it this weekend.
This morning, while driving, I paid a little extra attention to where I felt the vibration was coming from, and I think it felt more like the rear.
Heck, for all I know, last time I got brake drums, they might not have been balanced.

I'm thinking of putting the rear up on jackstands and have my wife slowly accelerate while I look everything over to see if I can see any wobbles. Might be visibly obvious.

 

Year before last I had a u-joint go out which caused the pinion bearing to go out. Or the other way around. Not sure. There was NO play in the driveshaft until I unbolted it to check. Thats when I found a bad u-joint, and a LOT of slop in rear end yoke. But the symptoms were a bad vibration, until it got really bad.

 

Alright, Friday I had had enough, so I took it down to the tire shop to have them look it over. The guy, aside from going bonkers over my bronco (which was fun) took it out for a test drive to feel the shake.
Afterward, he put it on the rack and looked everything over.

Issues:

Both ball joints on the front driver side are worn.
Both axle pivot bushings need to be replaced.
Driver's side needs the wheel bearing tightened.
The large drag link is worn.

Everything else was tight as a drum and in great shape. Drive and u-joints lines were great.

However, he said that none of that would cause the shake and that it's coming from my rear tire(s). I have retread tires from https://treadwright.com/ which I've had great luck with, and they have balance beads in them.
He couldn't find anything visibly wrong with the tires, but just suspected that maybe the casing was bad or that the cap was coming off, but had nothing to back it up with except suspicion.

I suppose I can try swapping the tires out one by one for a spare to see if I can get rid of it, but I wish I had something more firm to go on.

Thoughts?

 

Taking it to a tire/ball joint guy guy would give the expected recommendations. Of course nothing is better than round tires.
If you really thinks it's tires, it's easy to take them off and put them on the spin balancer. Anything should show up there.

 

Sorry, I forgot to mention that we discussed the rear seal. It was dry when we put it up on the rack. I have an oil leak I'm working on sealing up and after 600 miles of our trip last weekend, the differential was just covered in oil from it spraying back. The seal was fine.


As for the tires, is it possible to spin them for out of roundness when they have 6 oz of balance beads in them?

 

when you first run them up on the machine, you can see high/low spots. Back in the day you could buy tires and get them "trued" at the same time..not something people do anymore I don't think.

I bought a new set of Goodyear's for my 67 Camaro once..one tire was bald on one side before It trued up. Of course they tried another and it was better, but some rubber came off all the tires..Of course that was the 60's and things are much better now.....?

An old rule of thumb used to be, things don't really show up bad till you reach 60"mph...and if ur gonna drive 70-80..they better be round and balanced. Now in a 4x4 with BIG meat...another story...

 

That makes sense. This weekend, I'll swap some tires around with my other Bronco and see if it goes away. If it does, well, there's my answer.

You can feel it start to shake at 3mph. The shake is about the same from 30 - 60. 80 is actually smoother, but maybe its' because it just sort of all blends together. I'll keep digging.

 

One other thing I forgot to mention. Sometimes I'll just have smooth "moments". Maybe 5 - 10 seconds where there's so much less shake that I wouldn't notice it if it wasn't supposed to be there.
Or some days where the shake is just predominantly worse than others.

Who knows, maybe that's the front end weighing in a little bit?

I plan on dealing with the front end here soon, so we'll see what that eliminates.

 

easy way to check round on the tires is to jack it up just enough for the tire to skim the ground and rotate it slowly, it there are flats or bulges you will find them. I did this on my tires and found the flat within seconds.

 

Thanks for the idea. I wouldn't have thought of that but it makes a ton of sense. I'll try that.

 

and doing this one side at a time can help reveal any side-gear/outer wheel bearing issues possibly ..of course you cannot have "posi" for one wheel at a time..the good news, you can mimic 60mph at lower drive-line speeds...

overall good luck..

 

at 80..hopefully you're backing off the throttle?...and hence more "float" though-out the drive-train..

 

Subscribing. Hope ya get it Bud.

 

Pivot bushings are a **** to do... just save yourself the aggravation and take the pivot arm off, all the way to the coil and radius arm (you did check the radius arm bracket for cracks, right?). Unbolt the coil, radius arm, shock/s and pivot bushing, then beat the hell out of it or press it out.

 

Well, I jacked up the rear end just enough to spin the tires. Both rear tires would have parts of the rotation that would "catch" while they were spinning and rub against the ground while other parts of the rotation would freely spin. It wasn't super noticeable, but there's definitely some high spots. No idea what would be considered normal, or out of round.

I'll be ordering all of the parts for the front end rebuild here soon. I remember doing the axle pivot bushings before with my Dad about 10 years ago. The hardest part that I remember was getting everything lined back up to get it back together.
The local shop wasn't about $200 to do it. Not sure if it might just be better to go that route. =/