Like most of you guys out there, flogging our cars at track events is only part of the equation. Hitting the open road and laying your foot down on lengthy cruises is just as gratifying— especially in homebuilt sleds. With cruising a priority, the secondhand TH350 we used in our ’72 Nova project car was a great companion, though not without its own shortcomings. The stock converter made launching the car out of the question and with only three forward gears and no overdrive, it lacked the ability to sustain modern freeway speeds without laboring. This caused road trips to be spent mostly in the slow lane at a moderate pace and also meant frequent trips to the gas station.
We needed a transmission that could do it all, and support any future engine upgrades we had in mind without worrying about reliability. Plus, the Nova had to be able to handle long cruises while producing moderate fuel economy and able to boogie down the quarter-mile.
Since the engine was removed for its own separate upgrades, it served as the perfect opportunity to scrap the tired TH350 and lame converter for an all-new transmission. Through Gearstar, we sourced a 200-4R overdrive transmission outfitted with their Level III internals and a 10-inch 2,800- to 3,600-stall converter—good for up to 500 hp and 475 lb-ft. It all came shipped complete to our door in a crate and included the Lokar installation kit, ATF transmission fluid, heavy-duty shroud, and deep transmission pan. The 200-4R offered up more response from a dig with its steeper gearing, and the overdrive (0.67:1 ratio) would accept highway cruising with significantly lower rpm. Best of all, the swap required little modification since the overall case length is nearly identical to the TH350 we pulled out, which meant we could reuse our factory driveshaft.
To get it all in, we did have to swap out the factory transmission crossmember. Lucky for us, G-Force Performance makes a complete bolt-in crossmember kit to get the job done. While removing the old drivetrain can be a small feat, it’s nothing a seasoned wrench-turner shouldn’t be able to handle. In the following pages, we’ll show you what it takes to make your transmission upgrade as easy as possible.
G-Force Performance Crossmember
When compared to the factory crossmember, the difference is obvious between the G-Force piece and the stamped unit; it saved time and any unneeded fabrication. Each crossmember is built with performance in mind and designed with large exhaust clearance humps for aftermarket systems. A durable black powdercoated finish means it’ll last the lifetime of the vehicle and all crossmembers come with new 7/16-inch hardware and correct transmission mount.
Gearstar 200-4r level III
Upgrading to the 200-4R will keep the rpm low and potentially bump fuel mileage on long hauls. Moreover, the Level III is bulletproof and rated to hold 500 hp and up to 475 lb-ft of torque, making it the perfect candidate to handle our engine upgrades.
• 10-inch stall converter with custom-built lockup and billet cover
• Master overhaul kit with Raybestos Stage 1 racing friction and hardened Kolene steels
• Wide carbon-fiber intermediate band with reinforced wide anchor
• Stage 2 TransGo recalibration shift kit
• New valvebody separator plate
• Heavy-duty billet servo
• New Torrington bearings
• High-capacity 10-vane pump assembly with new rotor and slide
• New vanes and hardened rings 0.500 boost valve
• Updated pressure regulator valve
• Hardened 300M input shaft
• Forward drum with 300M hardened shaft
• High-performance extra-capacity direct drum assembly
• New speedometer drive gear and driven gear
Unlike some drivetrain removal,...
Unlike some drivetrain removal, the Nova’s platform allows for the extraction of both the engine and transmission as one unit. Using an engine hoist, we picked the combo out by placing the Nova on jackstands, creating additional room for the tailshaft of the transmission to exit at a steeper angle. To pull the drivetrain, we removed the hood—even the hood hinges. The mechanical fuel pump, battery cable, ignition wires, motor mount bolts, driveshaft, transmission mount, power steering, and radiator hoses were also all removed to free the combo from the engine bay.
Using the small access holes...
Using the small access holes in the front subframe, we removed the bolts that attached the factory transmission crossmember. We used a 9/16-inch socket and then slid the crossmember out.
To install the new crossmember,...
To install the new crossmember, we first enlarged the holes in the subframe from 3/8 to 7/16 inch with a drill bit. Next, we slid in the new crossmember over the exhaust and bolted it into place using the supplied Grade 8 hardware.
Going the extra mile, Gearstar...
Going the extra mile, Gearstar has thought of everything to make the 200-4R swap a cinch and even included a Lokar installation kit. The kit comes with a flexible fill tube and stick, throttle valve pressure cable, and carburetor bracket.
Not ready to swap out for...
Not ready to swap out for newer transmission lines? Lucky for us, the TH350 lines are a direct fit to our new 200-4R. We secured them into their new location on the 200-4R with a 1/2-inch flare nut wrench. Using the old lines with the rubber hose (inlet/return) will allow us to at least get the car back up and running again before we bend our own custom lines at a later time. Note: Transmission fluid is highly flammable under pressure (up to 250 psi) and rubber transmission hose lines are not advised for long-term use.
To change it up a bit, we...
To change it up a bit, we went ahead and installed the transmission by itself. To do this, we placed the Nova on jackstands and slid in the new 200-4R from underneath the car.
To simplify the crossmember...
To simplify the crossmember swap, we relied on the G-Force transmission mount; it’s a polyurethane piece and came with all-new hardware and washer plate.