Rear gear help?

Stay away from it. or
take the cover off and look.
The SureGrip has NOTHING to do with turning torque. Something ELSE is causing it to turn hard.
It could be as others have said,
or the rear end could be bent, as in the four reference points not being in alignment. The four points are the two axle-bearing housings, and the two case-bearing saddles.
Or
I suppose somebody couldda filled it with STP, or sawdust,lol.