[Fred Lee]

Rory,
All COPO Camaros and DragPak Challengers do use Strange engineered and NHRA
accepted 9 inch Ford straight axles similar to the Cobra Jet Mustangs. The 12 bolt
HammerHead I.R.S. that I make will be legal in Gen 5 Camaros that are in the NHRA
stock car classification guide but it is not used under any COPO Camaros.

Big Block Corvettes were known for breaking the weak factory I.R.S. rear ends but Tom's Differentials has developed many parts that will last. My goal was to make a 12 bolt aftermarket casting that will accept the 9310 alloy gears in all the popular ratios, 35 or 40 spline spools and whatever other heavy duty driveline parts that are currently available.

I have not tested the power loss between a "straight axle" and an I.R.S. but the first test car for my 12 bolt I.R.S. was also the first test car for the Driveshaft Shop's 9 inch
Ford fabricated I.R.S. We used a chassis dyno to compare the power loss at the rear
wheels. The horsepower numbers were 780 for the 9 inch Ford and 800 for my 12 bolt.

It has always been rumored that 12 bolt made 3% more power than the 9 inch Ford
because the pinion is 3/4 of an inch further away from the ring gear centerline than the
12 bolt. (1.50 vs 2.25 inch) I do remember seeing 12 bolts installed under SSA/A Hemi cars to replace the Dana 60 also. Fred Lee