Build a TH200-4R For 1,000 HP

The 2.350 diameter of the stock Second gear apply servo (right) limits its ability to apply pressure on the Second gear band. Carr solves the matter with his billet aluminum Super Servo (PN 12279). At 2.725 inches, it has more surface area than even the scarce Buick Grand National unit. The Super Servo holds the Second gear band with more clamping force to increase life while delivering crisper 1-2 upshifts.

Carr is not a proponent of lockup torque converters in high-performance applications. He says OE lockup clutches lack enough surface area to harness real horsepower, aren't worth the weight penalty, and sap power and dull throttle response due to the added mass. The finger points to the machined composite spacer that's installed inside CPT's 12-inch nonlockup converter in place of the clutch assembly (on left) that weighs 9 freakin' pounds. This CPT 12-inch converter has a 2,200-stall speed and is intended for use in 450hp street machines.

CPT also offers 9- and 10-inch nonlockup torque converters for the 200-4R. Here, converter assembler Juan Jimenez gets one ready for final assembly. In the case of CPT's 10-incher, careful selection of internal parts-particularly the stator-results in a torque converter that can handle 800 hp, stalls at 2,800 rpm, yet still delivers efficient highway cruising at 1,800 rpm. It's a favorite with Carr's Chevy 502 and 572 customers. The all-out 9-inch converter offering stalls at 3,500 to 3,800 rpm, but its stator design is efficient enough to cruise at much lower rpm in Overdrive.

Getting back inside the transmission, when a 200-4R is used with a nonlockup converter, the check valve and seal located in the end of the input shaft must be removed (left). These parts apply the lockup clutch feature in a stock transmission but are unnecessary. A fringe benefit is there's now more fluid available to lubricate the planetary gearset. A stock lockup-style input shaft is shown on the right for contrast.

On the stator side of the oil pump, the stock lockup valve (right) is replaced by a machined steel valve (left) that redirects the hydraulic circuitry to suit the conventional (nonlockup) torque converter.

The stock pressure regulator, boost valve, and spring (right) are set to provide line pressure of 60 psi in Park and Neutral, 110 psi in Reverse, 120 psi in First, 130 psi in Second, and 60 psi in Third and Overdrive. To allow the transmission to capture up to 1,000 hp without slippage, Carr swaps in replacement parts (left) that double the stock line pressure and deliver up to 300 psi in First and Second. All the parts needed to convert a 200-4R to nonlockup status are available from Carr. Call for specific details for your application.

Testing on the transmission dyno showed the stock seven-vane pump impellor (right) can be responsible for pressure fluctuations, so Carr sells a 10-vane impellor (PN 17701) that boosts pump capacity by 20 percent. The extra pump volume assures constant line pressure, so the internal hydraulic circuits function properly under all conditions.

A cupped orifice plug is pressed into the 1-2 accumulator housing to close off exhaust oil flow for firm shifts. It's part of the CPT Hi-Tech valvebody kit.

The governor controls full-throttle upshift and downshift rpm when the gear selector is in Drive. The lighter the weights, the higher the shift points. Traditionally, the Buick Grand National governor (top) has been sought by 200-4R builders, but Carr goes a step further. By machining the weights, any stock governor can be altered to provide the desired 5,000- to 5,400-rpm shift points. The caliper shows how much is removed from the weight.

CPT's Richie Consoli performs final assembly on all CPT transmissions. Here he preps another 200-4R for duty behind an 800hp big-block. CPT can sell you a complete transmission or just the parts you need for your upgrade.

Every CPT transmission is tested for proper function on this dyno before shipment. That way, you just bolt it in and go.

The CPT 200-4R in Robbie Whitlock's 800hp Chevelle has seen more than 10,000 street miles. Whitlock says, "The best thing is how the 3,500-stall speed gives a great launch at the strip, but the overdrive makes the 4.10 gears feel like 3.73s. I cruise the freeway home at 2,000 rpm."

Carr is quick to point out that excessive heat can destroy any transmission, so an auxiliary cooler is mandatory. Whitlock's blower drivebelt and mondo radiator pose insurmountable packaging hassles, so this undercar setup was devised. Without the preset thermostat-controlled fan, it would be useless. If there's no natural airflow to cool the fins and tubes, you have to make your own. Trick fabbed aluminum brackets keep it all in place.

Improper throttle valve (TV) adjustment is another transmission killer. The bottom line is to make sure there's no TV cable slack with the carbs at WOT. Carr sells TV cable adapters for all popular carburetors. Dig the dual-850 double-pumpers.