Rear End gear Whine

Need your help. I have gear whine at 60 KMH, no other speed.
It only whines at a steady speed, if I add throttle it goes away, if I let off it goes away.

8 3/4 cone type , recently added suregrip to existing 276 gear set that did not whine at all before , so I am presuming when I put the ring gear on the suregrip, I did not set the backlash correctly.

I am thinking my Backlash is off. Any thoughts? adjust it for less backlash or more?

Thanks a bunch!!