Ever since I've lifted my Rubicon I've had a vibration that feels like it's coming from the front driveshaft at exactly 48mph. Goes away at 47mph or 49mph and is amplified if 4wd. I've changed gears from 4.10's to 5.13's and changed tires to 35's, the noise is still there, same mph. Vibration started immediately after I lifted it. To me, it feels like a front driveshaft vibration, but with all of these t-case failures I've been seeing, I'm wondering if it isn't related to that? Anyone have the same issue? The reason I'm thinking possible t-case is because that with 5.13 gears, the driveshafts will be spinning faster than with the 4.10's and the vibration is still the same. I've serviced my t-case 5 times with synthetic fluid and everytime the fluid is cherry red no matter how hard I beat it, so it definitely doesn't show any signs of bearing failure or damage. I've also lifted my friend's Rubicon with the same exact setup and no vibration on his. Thoughts?

 

as you've pointed out, with 5.13 gears, your front DS will be spinning much faster and, if your DS is out of balance and/or you have too much caster, IT will vibrate.

 

just take it off and see if the vibration goes away..... its only a few bolts...

 

What kind of front drive shafts on the two Jeeps?

 

I've been running 5.5 degrees caster as it seems to be a happy median, but I'm also running the same alignment specs on my friends Jeep with no vibration. Guess it could just be a crappy, flimsy, stock front driveshaft

 

Stock front driveshafts

 

More than likely a tire balance prob, if it's speed related and you can go past it. Same thing on mine, removed the front ds and still had vibes, was a tire balance prob. Usually a ds vibe will start and increase with speed. Also with a stock ds the chances of vibes are slim because of the joints on it, unless you've knock off a weight or it's fixing to go out.

 

the first time this started, I had 33's. I now have 35's and rotating or balancing makes no difference. I work in a shop so I can balance them myself

 

Remove your front ds and go from there, possibly could be the rear, since you have a 2dr. If it's not either, you have a balance, rim or tire prob. My wife's lj tires were perfectly balanced, still a vibe/shudder at 50mph, ended up being the tires themselves, it happens.

 

RE-read post, you had 33's and it was doing it then too? You may have thrown a weight on the ds. Check for blank spots where a little square would be.