Need some input on a problem

[Crawler Nut]

Hello everyone. I just bought my wife a 04 Jeep Wrangler, It was a one owner with 65,000 miles. Older man had it, an is in great condition, The jeep was completly stock an she wanted to put a lift on it. Me an a buddy of mine that has done lots of lifts an built buggies installed the lift, it was a Rough Country 4 inch 2.0 lift. We did the T-Case drop an everything. Put on a new set of 35/12.50/15 BFG KM2
My question is when you are running about 60mph there is a roar an vibration that is terrable, but when you let off the gas the noise an vibration stops, when you get back on the gas it returns.
I called Rough Country an they told me it was probably the rear U-Joints well I replaced them an took it for a interstate run an it is still doing it. If it were the tires it should do it when you let of the gas correct? Any help diagnosing the problem would be greatly appreaciated. Thanks

 

[Chris_M]

might need an sye and cv type rear driveshaft

 

[amajeepman]

X2 for an sye and cv shaft. Mine did the same thing. Some get away with a tease lowering kit and some don't.

 

[rodney eppes]

Sounds like it could be pinion angle, causing driveshaft to vibrate. Must be right at the limit; under power- exceeds limit, deceleration- drops back in limits. Might be cheaper to experiment with pinion angle.

 

[BERTIE RENEGADE]

^^^^^^^^^^^^^^^^^^ all the above I would start with pinion angle

 

[upnover]

MEasure the angle at the t case output, and then the angle of the pinion. Need to be the same. I think all these guys are pointing you in the right direction.