3.91 sure grip

Hello All,
This is a general question,since the 8 3/4 i am refering to is not in an A-body.
I installed a 8 3/4 ,3.23 clutch type sure grip,742 case, from a A-100 van into my truck.It was/is a good third member but i wanted lower gears so i changed it out with a 489,3.91 clutch type sure grip,and new yukon axles with the green bearings installed.
turning on to the street from my driveway,i noticed that the rear end acts like it has a locker or spool or welded spiders in it.
the 742 with 3.23's did not act that way.does that mean something is wrong with the 489 case,or does it mean that the clutches in the 742 diff.are worn out?
thanks
Clark