should be able to see the collar nut on the top of the box from up top without removing anythin. Best way to adjust the box on I-6 car's is from up top. Easiest method to break the collar nut loose is with a universal and two long extensions to up top...hard to get leverage with a box end from down at the box. Be sure to scrib a mark in the end of the allen adjustment screw before you loosening the collar nut.
HTH,
George