I've got a 9in rear end out of a 1977 Thunderbird that I'm using in my 52 truck. When up on the lift the driver side wheel spins nice and easy whether turning the wheel or the yolk. The passenger side does not spin when turning the yoke and when turning the tire it is very stiff. But when I turn the tire the yoke spins. I've rebuilt both of the brake systems and the parking brake is disengaged. I haven't taken the pumpkin apart yet to see if there is anything obvious inside of it, and I'm basing the non posi assumption off of the tag affixed to the rear end. Is one side being tougher to spin than the other normal for a non posi rear end? Or is there something possibly wrong with the rear end?
Could it be that the axle housing is bent on the passenger side causing the bind? Just tossing out an opinion as that might stir interest from more capable people. These housings are often bent- 42 years.
Drum or disc? If it's drum, first take off the drum and see what happens. If it's disc, take off the caliper and see what happens.
The problem is in the axle, brakes or bearing in the side that is difficult to turn. As Squirrel said , start with removing the drake drum, to eliminate the brakes, if still stiff, check the axle bearing, if ok, check alignment of housing. Bones
Just went thru something similar. All new brake hardware and new drums. It turned out one of the new drums was not machined quite deep enough and squeezed the shoes against the backing plate. I put the old drums back on and all was fine.
I had a stock one out of a big Lincoln that one side was hard to turn. I am not sure what the deal was as in why it was the way that it was but it eventually turned out that I needed a little shim between the backing plate and the axle end. When tightened down the backing plate was binding the bearing.