Any thoughts on why my sure-grip did this?

Car info: 72 duster-318,mopar purple cam 340 repo grind,headman headers,2.5 exhaust with x-pipe,street demon 625cfm carb,and edelbrock performer intake.904 trans stock

3rd member Info: 489 case 3.23 gears..


A friend sold me a a-body 8 3/4 for my 72 duster and gave me this 3rd member for free.But my question is it safe to drive it like this or should i replace the sure-grip unit? And also if there's cheaper alternatives to the sure-grip units?

Or will it just be cheaper just to buy another 3rd member because I really want 3.55 or higher gears? Thanks