Evan J. Smith said:
More than just a fancy add-on, JDM, JPW, MW, Moser, T/A, Strange, and Summit girdles are made from strengthened aluminum and feature thick flanges, structural bracing, and fill and drain plugs to simplify fluid servicing. These aftermarket girdles are also a bit larger than standard covers because it helps them clear larger ring gears and allows for an extra half quart of rear fluid. Yet the real benefit to any girdle lies in the two load bolts that are integrated into each design. The load bolts can be seen protruding out the back of the covers; I'll explain their purpose in a moment.
During a drag race launch, the pinion gear is smacked into action, and it slams the ring gear and sends it into motion. At the same time, the torque delivered by the engine, transmission, and driveshaft drives the pinion, ring gear, and differential rearward. In simple terms, the force tries to smash the differential out the back of the rear housing. The loading is only resisted by the main caps, which hold the differential in place. Often, the force is severe enough that it distorts the main caps and causes them to crack and fail. The loading also causes the ring-and-pinion gears to spread apart from each other, leaving the skinny ends of the teeth in contact, the result of which are broken gears.
The good news it that aftermarket girdles are stronger than stock stamped-steel covers found on most factory rears, and, as I mentioned above, they benefit from the loading bolts that are fitted through the covers. Each of the two loading bolts has a swivel foot on the end that butts up against the center of the main caps and preloads the cap to counteract the loading seen on launch or hard acceleration. Though the system sounds simple, it has a wonderful effect, often increasing the longevity of internal parts.
When installing the new cover, first run the load bolts out so they don't contact the caps, then install the cover and torque the retaining bolts to the housing. Next, run in the load bolts until they contact the caps, then torque them to 5 to 10 foot-pounds (the exact specs vary per manufacturer). Believe it or not, that's all that is required to apply the proper amount of preload. Last, lock the load bolts into place with locknuts.
I hope I'm not shooting myself in the foot when I say that I've run a T/A cover on my Stocker since 1995 and have been never had a rear breakage. As do most stick cars, my Mustang tends to wear out a ring-and-pinion every few seasons, but the Royal Purple fluid always looks good, and things pretty much stay in check. I highly recommend a rear-end girdle on any strip or high-performance street application. It's a nice way to cover up any rear problems that the car may experience.
Evan J. Smith is the tech editor for Muscle Mustangs & Fast Fords and a contributor to High Performance Pontiac and GM High Tech Performance magazines.
Copyright National Hot Rod Association Aug 29, 2003
Provided by ProQuest Information and Learning Company. All rights Reserved
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or just 
, and i was just about to ask what the 2 bolts were for.
