Rear-end vibration (1 Viewer)

[Relativity]

So after getting a set of fuel offroad wheels + KO2s, I started to feel vibration at 60-65 mph, I can see the passenger seats shaking, but the steering wheel is not vibrating at all. I asked the store to rebalanced the wheels and tires, it didn't help. I put back on the original wheels w/ open country II (lighter than the fuel offroad wheels) the vibration is there, it's more subtle so I didn't notice it before but if I pay attention now I can feel it. So looks like the heavier new wheels amplified it. There is no noise, just up-and-down like vibration, and it happens no matter if I am accelerating.

I've replaced the two busted outer tie rods, checked the driveshaft and the u-joints there is no play. What are the next things to check?
1. driveshaft balance
2. wheel bearing
3. engine mount (very unlikely right)?

 

[tingc222]

A road force balance might be in store as a first step, given the history of it starting after the new wheels and failed regular balancing.

 

[Thed351W]

Did you check the driveshafts when parked, or with the trans in neutral? If you checked it in park, then you'd have tension in the driveshaft, since the trans is holding the vehicle still via the driveshafts.

Correct procedure would be in neutral with the parking brake engaged. You should have at least felt the free play in the differential.