Moore yanked the original open differential and installed the new Auburn. In our case, for some unknown reason, he had to completely change the shim-thickness package to dial in the proper backlash. Ratech supplied the installation kit, which included all new differential bearings.
There are only a couple of companies that offer a limited-slip differential for the Olds 8.2-inch 10-bolt, so we went with Auburn, which is a cone-type limited slip.
Drivetrain Details
Moore also saved the TH400 out of the Olds Delta 88, and his pal Steve Bunch resurrected it with new clutches, a TransGo shift kit, and a simple spring change to increase the line pressure at wide-open throttle (WOT). Trans guru John Kilgore also encouraged us to include the electric kick-down switch that supplies 12 volts to the trans at WOT, which increases line pressure to firm up the shifts. This is a common error on TH400 trans swaps that can eventually lead to burned high-gear drum clutches.
For the rearend, Moore decided to stick with the original 8.2-inch rear-axle assembly, and later, we popped for a new Auburn limited slip from Moser while retaining the stock 3.36 rear gears. Of course, as soon as the new Auburn arrived, Moore ran across a used posi at the swap meet for $100, so our timing was weak on that one. But the good news is we now have power to both rear tires.
Olds 8.2 axles are retained by a four-bolt flange instead of the more common C-clip used in other GM 10- and 12-bolt rearends. The information we gleaned from the 442.com Web site indicates the axle bearings are also suspect. Ours were in surprisingly good shape and did not need replacing. The big limitation on the Olds 8.2 10-bolt isn't really the gears as much as it is the 28-spline axles, which are not close to being strong enough if we ever hook all the 455's torque to the track with sticky tires. Eventually, we will need a 12-bolt to add durability. But for now, consider this a 10-bolt durability test.
This is the final assembly, all torqued in place and ready to rumble. The discs require a minimum of a 15-inch-diameter wheel, but why would you be running 14s anyway?
After enlarging the spindle-mount bolt holes in the Olds steering arms, we torqued the spindle bolts in place.
Bigger Brakes
A common swap with these early A-bodies is to dump the rather puny 911/42-inch front drum brakes in favor of '68-'72 Chevelle disc brakes. While we considered searching for a set of used disc-brake spindles and then piecing together rebuilt calipers with used or new rotors, we made the swap much easier and went for a completely assembled disc-brake conversion kit from Original Parts Group. The kit comes with the spindles already loaded with packed bearings, new seals, new rotors, and new calipers with pads. The package also comes with new flexible brake hoses, spindle nuts, and dust caps. The only change was to swap on our Olds steering arms. This required us to drill the original 71/416-inch attaching bolt holes to the newer 11/42-inch disc-brake spindle size. This beats the hell out of chasing down those little parts all over town, and the price difference was minimal.
We also replaced the stock single-reservoir master cylinder with an orphan '70 Chevelle master we had in the garage. All we had left to do was to plumb the Wilwood adjustable-brake proportioning valve into the rear brake line and the brakes were complete. This is where we learned a valuable lesson. In an attempt to make the brake lines easier to make, we plumbed the rear brakes into the front master cylinder outlet. At the time, we didn't think this mattered, despite knowing all GM cars are designed to actuate the front brakes with the forward-most portion of the master cylinder-designated the primary piston. We immediately ran into a problem where the master would not make pressure. We tried all sorts of solutions until our pals at Stainless Steel Brakes told us to switch the master cylinder outlets so the rear reservoir actuated the rear brakes. As soon as we did this and bled the system, we had instant pressure and solid brakes. We'd rather not admit how much time we spent trying to figure it out.