Fastruck Rearend - Beginning The Build

Fastruck is a regional paved track touring series. Although they resemble the trucks in the Craftsman Truck Series, Fastrucks are more akin to street stocks underneath. This is what keeps this class affordable. The Five Star body is a combination of aluminum, molded plastic, and fiberglass parts. The Dave Pletcher chassis begins life as an '81 Monte Carlo metric frame of 108 inches. The Bullet Performance Engines 305 Chevy mates to a TCI transmission. Altogether, this is a wolf in truck's clothing.

We tried to gather as many parts as possible before starting construction. It took quite an organizational feat to accomplish this. I ordered parts that I thought would work, and this made me do my homework more carefully. Soon my shop began to look like a parts warehouse, and construction finally began.

The chassis, which we had first seen when it was fresh from the donor car, was soon on a chassis jig at Dave Pletcher Racing's shop. The crew attacked the chassis with various tools, including a big MIG welder. Straight tubing was soon made into the shape of a racing chassis. Pletcher has made a number of winning chassis in the Fastruck Series. With a store-bought chassis like this, you can get replacement parts as well as setup information. I found the Pletcher chassis to be well constructed. The design is well braced and appeared to have the one thing a chassis needs-stiffness. It certainly is a safe chassis design.

When Pletcher Racing finished the chassis, it went on our trailer and was on its way to the powdercoating shop. Two days later, we picked up a beautiful silver metallic chassis, and it was on its way to finding a home in my shop for a couple of months.

The first thing we did was put the chassis on jackstands. Then we used shims to level it, which created good reference points for all the work.

Our next project was to gather and assemble all the parts for the Moser Engineering 9-inch Ford rear. Moser uses a stronger housing than some I have seen. The pumpkin, chunk, center section, or third member-whatever term you prefer-also came from Moser with a light steel spool locating the ring gear to mate with the pinion. The 31-spline axles with splines on both ends are stronger than the OE flange axles. Since this is a floater rear, it was machined and threaded at the outer ends of the housing.

In case you are not familiar with a floater rear, let me explain. In a standard rearend, the axle that powers the car also carries the weight of the rear of the car. With the floater, in this case the Moser unit, the axles are splined on both ends. Hubs that carry bearings fit on the machined part of the housing. A nut threads onto the housing and retains the hub bearings. Now the truck can be rolled around; however, it can't do so under its own power because the axles are not installed. A splined plate then bolts to the hub. The axle is fed through until its splines engage the splines in the spool. Then the outer splines on the axle will engage the drive plate. The truck can be driven at this point, but the axle could fall out. To retain the axle, which has little side-load on it, a small plate is bolted to the drive plate.

The description of this process sounds more complicated than a standard axle setup. In practice, it is not difficult. The floater setup is also much stronger and safer. If an axle breaks, the wheel cannot come off, as in the case of a wheel bolted to an axle flange.

In preparation for the rearend assembly, we made sure we had all the necessary parts. After carefully packing the hub bearings with grease, they were placed on the housing. Packing the bearing means more than smearing grease on the outside. To pack a bearing, use palm pressure to force the grease down inside and between the rollers. There is a tab washer that goes on before the nut is attached. When the nut is sufficiently tightened, a tab is bent into a slot in the nut to locate the nut. Don't force the nut onto the threads, because it has a large diameter with a fine thread that is easy to cross-thread. It should go on with your fingers. Use a spanner wrench to tighten the bearings until they have some drag. This sets the bearing. Back off on the nut until the hub turns freely, and then set the tab into the nut. Moser furnishes a seal that goes inside the axle housing, and it should be installed snugly. This seal keeps rearend lubricant from sloshing to the outside and away from the gears.