Sure Grip or not

ok it actually happen more then once and the gears are either a 3.23 or a high 2 something. I check the gear ratio a whille back by jackin up both rear wheels and countin the number of times the wheel rotated and the yoke. i actaully checked twice one only rotated backwards the other time both wheels rotated the same direction. I'm askin because i want both wheels to pull u might know that. But i was about to buy a locker but if it has a sure grip i don't need a locker i just need a rebuild kit right. I guess i'll just pull it first and find out. I have to many projects!!!!!!