GM Upper Control Arm Knock-Out Tool Here�s the tool you need to remove the inserts on the upper control arm alignment brackets of light-duty GM trucks. It features an indexed forcing bolt that pulls straight and evenly, and works with off-center knock-outs. The tool fits 1989�2001 Chevrolet and GMC 1/2-, 3/4-, and 1-ton trucks, two- or four-wheel drive. Also works on 1990�2001 all-wheel drive Chevrolet Astro vans and GMC Safari vans. No. 7491C � GM upper control arm knock-out tool.