Differential is making noise

I change the crush sleeve and still made the soundi know now is not the crush sleeve nor the piniion depth has good backlash and ring is adjusted to pinion good…how ever there is one last thing nd thats the cross pin you think that would make a difference i bought one from ebay looks round andi n shape of a cylender however the one i took off that waa bad had flat edges two in each side
You think that would make the sound

Fixing a whine in a differential is an art even for an experienced mechanic. I had a friend who worked at a GM axle plant. Some differentials whine right off the assembly line.

His full time job was to disassemble, read the gear pattern and fix them. If they were still noisey they went to the smelter.

If you really want to change rear end ratios the best way is to buy a used drum to drum rear axle with the ratio you want.