whining rear

You said you bought a center section, and checked the backlash. You can run a pattern as long as you can see the gear teeth... The seal can be replaced with the carrier in or out. I find it easier with it in. It sounds like you may have overtorqued the pinion nut. 741 is not a crush sleeve rear and I torque them lower. Usually around 180. But the only way to know is to pull the centerestion, run the pattern, and verify it still has .010 backlash.