Ok, so here's the deal. For months I've been getting a vibration. Not a quick vibration, but not a slow one either. Most of the time something has to set it off like me going around a turn or hitting a bump or something of the like, and it only happens at ~65mph and over.
Part two is, the other day on the interstate at 75+mph I started hearing a chattering sound. My first thought was immediately the front driveshaft because that would make the most sense coupled with the vibration. I got under her later that evening after she had cooled down (in the dark) and tried to wiggle it around. Surely enough, there was a little play. She still had three hours worth of driving ahead of her, so I grannied her the whole way. I checked again once I had some light and the drive hadn't made anything any looser. I also noticed it was the output shaft on the transfer case that had some play, not the U-joints. I went and checked the transfer case on my parts truck and its output shaft had the same amount of play, so I ruled that out as my issue.

So here's where I'm at. The following parts have been replaced recently and therefore have been ruled out.

Drag Link
All Ball Joints
Front Drivers Hub Assembly
All other wheels checked for play, all bearings are fine

I noticed when I was under her that the track bar had a tear in the grease boot on the drivers side and it looked a little dry. I wiggled and didn't feel any play, but this is my primary contender right now. I will be replacing the whole bar in a few days.

Also, I tried to recreate the sound a couple separate times by getting her up to 75-85 mph and she wouldn't make the clattering sound any more. Not sure what that means, perhaps it will only do it after an extended period at those speeds.

Any other ideas you guys may have would be much appreciated. Thanks!

 

Anyone have a second opinion? Any ideas other than the Track Bar since it doesn't feel loose?

 

track and drag are good candidates
how worn out is your steering damper? that would be my first look

 

Steering damper is brand new also, forgot to add that to the list. Thanks Dusty.

 

Does the noise and vibe get faster or slower with speed or engine rpm's?

My thoughts initially were the CV joints on the front axle but they would be noisier when turning but I'd still put my money on checking those out especially if they are the originals.

It may also be a wheel bearing rattling around.

 

If that front drive shaft has not been rebuilt then it could be the culprit and should be done as part of preventive maintenance.. Any vibes can make something rattle sounding like the chatter you describe. I know thats a bit of a shocker with the stellar build quality of these vehicles.

 

I had a sometimes nasty vibration under the floorboards that I couldn't pinpoint for months. It happened only after a while, and only at around 100 km/h. Spoke with a few mechanics about that over a few months, until I raised the subject with an older guy who had seen it all. He said look at other less obvious things, like the exhaust line. It could very well be that it is getting into a cyclic resonance with the drive train when it's hotter, and maybe because the walls are thinner after having corroded for years, the exhaust line has more flex.

I do not mean to say that this is your problem cause mine was not a chatter kind of problem, but once you have looked at all the obvious suspects, then there are other things that could maybe be a contributing factors, and you have to look at them in a different light. Like engine mounts, fuel lines that rub against something, you know?

Anyway, sorry I can't help, but maybe this can push you in a different direction...

 

I had a tire that did that once. There was a nail in it when I hit a trail, and while I waded through muddy water. Well , the nail let water in, and the mud sealed it. Crazy vibration filled drive home.

 

Again, it might not be the answer but, I had vibes so rebuilt the front and rear propshafts and that helped a lot but didn't eliminate all the vibes. I then discovered a faulty ball end on the drag link so I replaced the whole drag link and that helped but still slight vibes at around 75-85mph so then I replaced the engine and gearbox mountings and the vibes disappeared completely I'm not suggesting this is your problem but it's strange how other things affect the chassis resonance and it's often not the obvious problems and can be driveshafts, wheel bearings, CV joints, diff bearings, transfer box or autobox bearings or even something as simple as an exhaust pipe resonating.

 

as some have mentioned, the engine and tranny mounts, Also I would have a look at the roto-flex. You would be amazed at how an older one can send vibrations thru the chassis.