[buzzinhalfdozen]

With the rear tires and brakes off in the rear , turn the pinion nut with a beam type inch lb. torque wrench you should see no more than 30 in. lbs of torque to rotate the rear end this measures both the pinion preload and side bearing preload at the same time. I'm more inclined to think the axle housing is bent at the ends and is creating a toe in condition for the rear tires which will make it very difficult to push. The gentleman who suggested you use a square and check for rear toe is most likely correct, it is a simple operation and will give you a definate result.Good luck Joe