In our last issue, we detailed the job of installing a Zip Products HD Dana 36 differential in our '96 C4 coupe. Although the installation itself went off without a hitch, all that loosening and retightening of suspension components exacerbated what previously had been only a minor problem with the Vette's rear ride height. Indeed, no matter how hard we cranked down on the stock spring bolts, the freshly modified car persisted in evincing the kind of arse-in-the-sky stance you might expect from a '79 Camaro running a pair of Gabriel Hijackers. Not cool.
To preserve our C4's handling balance and restore a measure of aesthetic respectability, we contacted Vette Brakes & Products in St. Petersburg, Florida. VB&P has been fulfilling the chassis and suspension needs of the Corvette market for more than 30 years, and today boasts what is arguably the most wide-ranging product lineup in the industry. The company sent us a kit containing a pair of custom-length lowering bolts and all the hardware required to install them on any '84-'96 model.
As we have so often in the past, we decided to farm out the work to AntiVenom, a highly regarded Corvette specialty shop in nearby Seffner, Florida. Although this is a job a skilled mechanic could conceivably perform in the driveway, access to a lift, an air gun, and a specialized spring-compression tool will reduce installation time considerably. In our case, AV's Greg Lovell and Casey Willard had the bolt kit in and the car's ride height set in just under an hour. Follow along now to see how they did it, and to check out the finished product.
With our C4's new rearend properly broken in, we day-tripped it up to Gainesville Raceway to see what effect the differential's shorter 3.54 gearset had on quarter-mile acceleration. The jaunt also afforded us an opportunity to see how the fresh ring-and-pinion affected the car's fuel mileage and driveability, the two areas that traditionally suffer most as a result of such installations.
Since the lower (numerically higher) gears promised to boost the car's off-the-line snap, we augmented them with a pair of Nitto's NT555R radial drag tires measuring a brawny 315/35R17. Unlike some of the other "drag radials" on the market, the Nittos feature a wear rating of 100 and a tread pattern that makes them suitable for occasional street use. (Just be sure to keep your Vette's traction-control system engaged in day-to-day driving and keep a close eye on tread depth, especially if you plan to use these tires in the rain.)