Sure Grip Advice

Your main Carrier bearings on the 3.55 gear set are probably wearing enough to allow the ring gear to start moving away from the pinion changing the Pinion to Ring gear wear pattern creating the whine.

You should be able to take your Cone Style Sure-Grip from the 3.55s and swap that over to the 741 with the Open 3.23 gear set. Along with a new bearing set and setup. Cone style Sure-Grips have 2 spider gears and the cones can wear out. The Clutch Style Sure-Grips have 4 spider gears making them much stronger and less slop in the differential as a result. Less "Clunking" when you drop into gear.