Moser Engineering Rearend - Safety Third!

So you're never going to guess what happened. Last time we went to the track with the Amsoil GT, it went so fast we got thrown out of the track and were told to never come back!

Sure we had a rollbar and five-point harnesses in it, but you need a lot more than that to go quicker than 10.00. So this is the first of a few stories on how to take your 10-second Mustang or fast Ford and make it legal for 9s--and we're starting with the rearend.

We haven't had any rearend issues with our '11 GT, which is surprising with nearly 700 rwhp. With no exaggeration, the rear was stock with a set of 3.73 gears and a diff cover. The stock differential and axles were still in place, and the stock rear brakes were still used with pads and rotors from EBC. The stock stuff is good! The posi is strong and the 31-spline axles can support some serious power, but with C-clips, if you break an axle, you're going to make a mess of the track if you lay down gear oil, or worse, lose control and crash.

To prevent any mishap, we called our friendly rearend buddies over at Moser Engineering for a little help. We threw around a bunch of ideas and thought about just putting a 9-inch in the car, but the 8.8 is good enough to go mid-6s in Outlaw Drag Radial cars, so we decided to keep it. We did have to figure out how to keep the wheels on it if an axle broke, and it came down to one of two choices--8.8 C-clip eliminators or 9-inch housing ends. Knowing that we wanted to upgrade the rear brakes in the process, the 9-inch (Ford Torino) housing ends (PN 7750, $95) made more sense, as more brake kits are available for this style--but more on the brakes later.

With the Torino ends picked out, it was time to figure out axles, and Moser made the choice for us. We went with a set of 33-spline alloy axles (PN A33CST, $370), not only for strength, but because we would be using Moser's 33-spline Wavetrac differential (PN 5W8833, $1,095). Yes, the Wavetrac is almost $1,100, but it's designed to be nearly indestructible. The body is made from case-hardened billet steel, the internal gears are 9310 alloy steel, and it's all held together with ARP fasteners. It even comes with a limited lifetime warranty!

You may be saying a diff is a diff, but that's not the case. According to Moser, most torque biasing differentials supply more power to the wheel with more grip, but in a zero axle-load condition (like lifting a wheel), the other wheel gets zero power. The Wavetrac is designed with precisely engineered wave profiles on one side gear and its mating preload hub. When the side gears begin to rotate, the waves climb each other, causing enough internal load to overcome the zero axle-load condition. What does this mean for you? More power precisely delivered to the rear wheels.

With the Wavetrac and axles in place, we shifted our attention to stopping. Moser supplied us with a set of its Dynamic Mount Performance Drag Brakes (PN 6200-12500, $645). These are compact, lightweight brakes designed for drag-race applications. The four-piston calipers are machined from 6061 T6 billet-aluminum and are anodized black, giving them a killer look.

The rotor and hat design is something new and different. The billet-aluminum hat is slotted, and the cross-drilled rotor has fingers that fit into the slots. The assembly is held in place with a spiral-retaining ring. This design allows for more radial growth of the rotor during high-temperature cycles, which helps reduce the sticking, warping, and beveling that can occur under heavy braking. The kit comes with Hawk HP-Plus brake pads, which are held in place with two pins.

We finished off our rearend build with one of Moser's aluminum differential covers (PN 7106, $149) and two and a half quarts of Amsoil Severe Gear synthetic gear lube. Soon the interior will be ripped out so we can weld in our new chromoly cage from S&W Racecars.