Driveline vibration

[moohart]

Where to start...

I'll start that I am not a novice with Jeeps, lifts, etc etc., but I am stumped. This issue started a few weeks ago rather abruptly. No recent mods or adjustments made, and due to the ongoing engine issues, this didn't happen after a wheeling trip. The truck has always driven very smoothly with no issues with vibration.

The Jeep:
21' Gladiator Rubicon EcoDiesel.

The relevant info (off the top of my head):

• 4.5" lift - yes the geometry is all good, never an issue for 30k miles.
• 40" tires, with RCV axles, trussed and gusseted.
• Tom Woods driveshaft
• regeared with Yukon

This sound is rhythmic with speed. It is definitely somewhere at or after the transmission. I jacked up each tire 2" and placed a pry-bar under each tire and gave it a pull and discovered that the wheel bearings on each side were going bad. I replaced those last weekend and the vibration and rhythmic noise were still there. Next, I dropped the rear driveshaft and replaced all the u-joints. Still have that rhythmic noise. VERY frustrating at this point. The vibration is subtle, especially at speed, but as I decelerate the noise is quite pronounced. It's not the tires, no cupping and the cadence is too fast for the tires, more like a driveshaft or driveline. Being that the u-joints are new, the wheel bearings are new, I'm thinking pinion bearing?

It's hard to diagnose because the driveline needs to be under torque and load. If you put it up in the air or put it in neutral while driving, it goes away. Reengage the load and the sound comes back. At this point I feel like I need to strap it into a dyno and lay under need it just to get a listen while there is load on the wheels.

I need some of you more drivetrain/differential savvy folks to let me know what I might be missing. To me, it has to be at the differential, transfer case, transmission. No issues with functionality of the transfer case or the transmission action shifting. Brake pads are not rubbing. The cadence isn't quite right, and I verified no rubs.

If we have any real experts on drivetrain and axles with any ideas, it would be greatly appreciated.

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[Rusty PW]

A lot of people don't like Yukon gears because of the noise they make at time. You are going to get a couple of replies on that.

Look at the front pinion bearing. Those had been an issue at times on regears. The cage is made of plastic.

 

[moohart]

Is there an easy way to tell if I pop the diff cover? I did take it off and do a cursory inspection just to make sure there were no big oh-crap busted teeth showing. I’m familiar with gear packs but not expert enough to try to install one. Shims, backlash and whatever else isn’t something I want to practice on.

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