Vibration help

I have a high frequency vibration that I feel between 50 and 60 mph. I feel it through the body of the jeep not the steering wheel.

4 dr auto

3 inch lift (actually got 4 inches because I don't have heavy bumpers etc.)

Stock control arms.

Stock drive shafts.

35's

New track bar, track bar bracket, high steer kit, tie rod, ball joints, wheel bearings, steering stabilizer, tires are balanced.

I have had this vibration for quite a while. It started after a wheeling trip a few months ago. Had other issues with death wobble and steering so I fixed all of that first. I think it is a drive shaft vibration. The rear drive shaft has been dented.

Any thoughts?

the cheap way would be to see if anyone has a spare DS they are willing to swap out with you. They still have a trail spare (with a slight dent) and you get to see if the DS is the culprit.

its dented and might be causing the vibs since you already addressed most of the other possible causes.

sounds like DS - we just did my front & back recently & got rid of 90% of mine...

I would think that if its the DS, it would be related to RPM's not speed. So look at what RPM you are running when it occurs. Then go out and put your trans in 2nd, and run up to that same RPM and see if you still get it.

The driveshaft, though, doesn't turn any faster or slower with RPM, right? It turns however fast it's getting output from the transfer case, and thus turning the wheels. If you're going 30 mph in a low gear turning 5k rpm the driveshaft will turn the same speed as going 30 mph in a high gear turning 1k rpm, right?

Correct

So, then...no RPM relation.

That would eliminate engine related vibration....so you are eliminating possible culprits. You are on the right track Eric...

I think on the Jk you have flange mounted drivelines? If so remove the front DS and drive it. Install the front and remove the rear, put it in 4hi and drive it and see what you get. Without the rear DS the transfer case can not bind up .... it will just be a front wheel drive. Just a thought...

If the JK has a rear slip yoke, you can also do it, but you need to plug the gaping hole around the output shaft, or all of the oil will pump out. If not, everything behind this will not rust.