Tom Wilson
February 4, 2010

The narrow OD band is replaced by a higher-quality, wider, 2-inch unit, and the line pressure is increased via drilling several holes in the valvebody plate. This firms the shifts, and other valvebody work allows safe full-throttle upshifts into OD.

Curing the weak, two-piece input shaft is accomplished by using a vastly stronger one-piece shaft. This eliminates breakage concerns, but the trade-off is that a lock-up torque converter can no longer be used. CPT makes its own non-lock-up converters, which is what Ricky received. This results in a gain of approximately 400 rpm at freeway cruising speeds, so fuel mileage may fall a tick, although historically this hasn't shown up much. The better acceleration and other efficiencies from the upgraded transmission probably offset the higher freeway cruise rpm-or rear-axle gear-ratio changes, power adders, and so on made at the same time as the transmission upgrade mask this relatively small effect.

CPT's 10-inch converter brings the foot-brake stall speed to 2,600-2,700 rpm, although CPT says you may see 3,000 rpm without creep on a sticky dragstrip and good tires.

Finally, a proper, high-quality 19-row oil cooler is fitted for the sake of dura-bility and consistency.

All told, CPT figures the average performance gain is 0.750 second and 3 mph in the quarter-mile, provided you have the traction. The increase in applied low-end torque is considerable, so the tires and suspension need to be up to the task.

As with all major improvements, getting this amount of work done costs more than just lunch money. The CPT Extreme Duty transmission retails for $1,999, the CPT Mega-Torque 10-inch converter is $549, and the oil cooler is $189 with fittings and brackets. Toss in tax, installation, and possibly shipping, and getting an AOD into shape can be a $3,000 proposition. The reward is a CPT transmission that will shift worlds better and happily bang out the thousands of shifts behind big-power engines.

Predictably, after driving it home, Ricky was excited about his new gearbox. The big deal is the fast, positive shifts in a streetable package. "It's not a neck snapper," he says. "It's solid, not laggy-just a good shift in all gears ... It has some stall to it-not too much ... It bangs the shift at 5,100 rpm every time at full throttle ... It chirps the tires at 4,600 rpm on the one-two shift. The car definitely feels faster and is obviously more responsive."

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