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TCI Transmission Upgrade - Putting Your Rear in Gear

Part I: TTP Installs A Brand-New TCI 4L60E In Our LT1 Formula

In the time spent trying to fix the LT1's misfire, we unfortunately missed our window to track test the new setup before Englishtown closed for the winter. Rather than sit idly by for it to reopen, we decided to head back to TT Performance in Passaic Park, New Jersey, to beef up the driveline. Since the 100,000-mile-plus 4L60E has seen better days, and a simple shift kit wasn't going to cut it, TCI Automotive offered up one of its Super StreetFighter 4L60Es to test, as well as a street-friendly Saturday Night Special torque converter. These two alone could significantly reduce 60-foot times, but what better way to put the stock LT1 into its powerband than with a 3.42 ring-and-pinion from Motive Gear? These notoriously quiet gearsets are perfect for daily drivers like the Formula, and its modest ratio will keep the Rs down for better gas mileage during highway driving, while still providing an enormous improvement over the stock 2.73s. In addition, the slipping stock posi was also canned in favor of an Eaton posi, which, unlike the stocker, features rebuildable clutches strong enough to last well into the 10s. For extra security, Moser hardened 28-spline axles would also be introduced to the refurbished stock 10-bolt. A TA Performance Differential Girdle and stud kit were the last prayers in keeping the puny 7.5-inch weakling alive.

While the fresh tranny and rear would provide both increased reliability and performance, they would not be able to assault the rear tires as much as the 3,400-pound Formula would like. To that end, BMR Fabrication was called upon for an adjustable torque arm, lower control arms, and relocation brackets to transfer weight to a new set of Nitto drag radials. The old combination, even with the headers and rocker arms, could barely spin the tires without power-braking-but with the new converter, gears, and BMR suspension components, I doubt this will be an issue any longer. The strong, tubular adjustable chrome-moly LCAs in the Street variation we chose have greasable polyurethane bushings and don't sacrifice a bit of ride quality. Similarly, the adjustable torque arm will enable proper weight transfer with its rock solid 1.25x.120-inch MIG welded tubing, and the adjustable nut will help keep the optimum pinion angle intact. Some may wonder why Nittos are the drag radials of choice, but consider three important benefits: they are the most streetable, they hook exceptionally well on the street (as well as the track), and they seem to be the best sticky tire to preserve the stock sized 7.625-inch ring gear.

Beefing up the stock 10-bolt rear may appear to be a futile task, but for an 11-second daily driver that only plans to use drag radials, why bother spending $2,000-plus on a 12-bolt? Now that the Formula has a tranny proven to hold more than 500 hp and the supporting suspension components, we will have to put power to it to see for ourselves how well this combo holds together.


BMR Fabrication
Thonotosassa, FL 33592
TCI Automotive
Ashland, MS 38603
TT Performance Parts
Little Falls, NJ 07424
Eaton Performance/Detroit Locker
Cleveland, OH 44114
Motive Gear
Chicago, IL 60609
TA Performance Products
Scottsdale, AZ 85260



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