Lock It Up! Install a Mini-Spool in Your Chevy

Racers have several ways to make both rear wheels of their stock car pull at the same time. Often track rules don't allow the use of limited-slip differentials. Stock-type diffs don't work well under racing conditions, and aftermarket units are expensive.

Another option is welding the spider gears in the differential unit. However, this has its own set of problems. For starters, the welds can break. I have welded a few and have had some gears break the welds. Remember, these gears are an alloy steel not intended to be welded.

Then I began to put more weld in and around the gears. This extra weld often put too much heat in the gears, warping the ring-gear carrier. This will show up as a tight spot when the pinion is rotated with no load. Additionally, it's easy to get welding slag in the gears and bearings. This slag, which is much like glass, can quickly cause wear in the bearings, leading to excessive clearances and rear-gear failure.

Full spools are available, but pricey. A full spool replaces the ring-gear carrier. It has no provision for spider gears and the axles are splined directly into it.

Perhaps the best alternative for the Chevy 10-bolt rearend is the use of a mini-spool. This consists of a set of four blocks. Two have a splined hole for the axles; the other two fit in slots in the first box to lock the two axles together.

Preparation

In our case, we had recently destroyed a rearend housing in a crash. This gave us an opportunity to start over on locking the rear. The gears in the first one had been welded twice.