So I have had this vibration for a long time now and figured I should look into it at some point. I seem to recall some people have fixed this with their driveshaft, is there a way to tell if it is bad without replacing it? What are some other things people have found with this issue? I did my front axle lube and it looked really good....I was just going to pump out my rear axle but I am now thinking I may want to pull the cover and take a look at the gears and bearings... Currently at at 70k.

 

I've been chasing it on my 2018 5L for several years and now at over 100k miles.
Recently had the drive shaft joints replaced. Seems a small improvement. My drive shaft had larger joints that were not available locally. A heavy-duty option on an Alum shaft OEM
Checked the shaft rear for out of axis rotation in place and found .014". Seems its within spec mounted in place. The shaft is also marked from factory in the same location.
Rear was down a Quart. Thought Dealer service checked it. No leaks. I now hear a slight wow-wow sound under light load like worn gears or bearings.
Put an additive in the rear and fill rest with regular fluid. Results seem a bit smoother.
Still have some 60 mph vibration.
The thinking is it's a rotation Harmonic that develops under engine loading from the suspension flex.
May be started from road irregularities.
The whole suspension geometry and dynamics I believe is the cause after a lot of thinking about the whole thing.
Vehicle loading with occupants also has an effect.
The rear springs have very little soft travel before the shorter leaf contact on the front Seperators causes a immediate shift to higher spring rate from either loading or road surface upward movement.
Engine Torque cases a downward angle at the end of the drive shaft, rotating the Axle housing. Only counter to this movement is the shock mounting Angle and shock resistance control to compression... This may be an area where a different shock might help kill off a Harmonic action if that is what is going on.
A lot of dynamics going on that all comes together at the rotation speed under some engine torque.
Almost think a road surface irregularity can start it off until speed is increased or reduced to get out of that Harmonic Resonance Zone.
A work in progress to see if I can find a fix.by changing something to break up the party.
Second set of tires balanced 3 times. It's not tires or tire location.
Put rear on jack stands and in gear to see if anything showed. Both tires running true to rule out Rims, Tires and Balance.
Note: on a 10 speed, trying to run rear up in speed has to deal with Trans upshifts. Any drive line slop is shocking to hear when shifts occur.
Also doing this can bring on Dash warnings for driveline faults and even set codes, so expect if trying this. Big reason is the system wants to see the vehicle moving on all 4s that its not doing with the rear on jack stands. Thats what causes all the system drive line anger.
IMO, the rear Pinion to Axles play is way too much but not going to do anything about it unless I have to. Hear or feel no roughness on complete drive shaft Ring Gear rotations.
My attention now is on tire pressure vs side wall flex and what it does to the issue.
Good luck.

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I put on new tires earlier this spring and I run winter tires, so that's 3 sets of tires all acting the same. I really don't want to tear my rear end apart for this but that is what the issue was on my 2006. when I'm going 60-70 I can't read the plates of the cars behind from the vibration in the rear view mirror. Seems like something I could really throw a lot of money at and still not fix and it will probably run another 100k without an issue....I don't plan to spend much time chasing this.....maybe this winter if I get bored I'll pull the rear apart and see how it looks inside and checkout the axle bearings.....but not likely

edit: my new tires are LT with a stiff sidewall for towing....it tows a lot better but no vibration change.

 

I just came home from shopping.
I made an Air pressure change just to the rear increasing it by 2 psi to stiffen the tires.
Seems to be smooth but not had a chance to get to 60 for any distance in traffic.
Going back out again and will test this notion out where I know the issue shows up.
Another problem is the wife has a Spine issue that needs softer ride. Between that and the vibration I have to stay with possible compromise.
We already use Jell filled cushions under seat covers that help a lot for general ride. Holding onto the steering wheel intensifies the vibration she does not feel as intense just setting.
Good luck.

 

If you have the 2-piece commonly found in the SuperCab (SCAB) 8' box, or SuperCrew (SCREW) 6.5' box, I'd recommend just replacing it. I fought with mine briefly before I started reading and the factory ones just aren't great.

https://fortwayneclutch.com/product/...onomy-version/

Put this in and haven't looked back. Took about an hour to do including changing the output seal on the transfer case.

 

I did the DS already, still have an issue like others - including an issue from a stop. No it is not the TC or trans - both are twice new.....dont ask.

 

This gentleman has documented this well. It is a combination of a soft transmission mount, harmonics from the 2 piece DS and soft rear springs/axle wrap. Raptor transmission mount and or leaf springs (or in someones case on the comments, Roadmaster Active Suspension) fixed the issue.

 

I have tried the raptor mount - currently I have the new "updated" mount (basically the raptor mount). I have a new DS. I will be putting in new leaf springs soon, along with traction bars to eliminate wheel hop/spring wrap. I have been chasing the bounciness from a stop for a while now.

 

that transfer case video is nuts. I really need a camera I witch while I drive like that.