Shift Enhancements for Your Automatic

Shift Enhancements for Your Automatic

Kick the slush out of your slushbox

The term "slushbox" was coined to describe the less-than-optimum shift characteristics of factory automatic transmission. All major manufacturers between the '50s and '70s offered mushy-shifting two- and three-speed automatics. To increase performance for non-standard uses such as towing or racing, automatics often received internal adjustments, machining and other refinements.

It's no longer necessary to drop the pan and access the valvebody to improve shifting.

Nowadays, automatic transmissions are more popular than ever. Computer-controlled four and five-speed autos are in countless vehicles. How can you enhance the shifting elements of a computer-controlled transmission? By tuning the computer, of course. It's no longer necessary to drop the pan and access the valvebody to improve shifting-the trans processor can be reprogrammed to alter shift points and firmness.

OE Compromises

The manufacturers' engineers must design transmissions that will be reliable in many different situations to accommodate everyone from the proverbial little old lady from Pasadena who only drives to church on Sunday to the tournament fisherman who tows his bass boat behind his "Cowboy Cadillac." So, actual transmission performance is muddled by other requirements like smoothness and ease of repair. The design must also be cost-effective to manufacture. The problem is that some drivers like firmer shifting, shift points at higher-than-factory rpm and quicker gear changes.

Modification kits and shift-improvement hardware are available for virtually every auto-shifter made, regardless of manufacturer, and for whatever requirement you have. These modification kits can be installed at home, and the resulting improvements are readily obvious. Whether sold as a complete trans-improvement package or as individual pieces, the end result is generally firmer, more positive shifts. For improved high-performance use such as towing or off-roading or for competitive events, the automatic trans can be built to spec with or without loss of driver/passenger comfort.

These upgrades (whether electronic or physical) rearrange the transmission's basic internal functions to provide crisper shifts. By eliminating soft and sluggish shifts, heat and friction are reduced, and less wear and tear on the clutch disks and bands means a longer transmission lifespan. Many of these aftermarket products are adjustable, which means that the transmission's shift points can be flipped to performance mode or back to OEM-style. All of this is installable without removing the transmission-most of the hardware bolts in after removing the pan or plugs into convenient computer ports in the cabin.

Other aftermarket kits permit shifting manually at non-factory-spec speeds. For example, most stock automatic transmissions refuse to downshift to First gear above 15 mph, and they automatically upshift at predetermined speeds no matter what gear the transmission happens to be in. Certain aftermarket kits allow the driver to hold the transmission in First gear indefinitely, which is a definite asset while towing a trailer or moving heavy loads downhill.

Shift-enhancement kits are relatively inexpensive and easy to install. To recap, these performance products will extend transmission life, can improve mileage (if your right foot doesn't overpower the gains) and will certainly increase the vehicle's "fun factor." Best of all, many of these upgrades can be adjusted to your specific style of driving. For an overview of how to install an internal improver, see "700R4 Shift Kit" elsewhere on this site. The photos here show how easy it is to add a switch-activated computer-recalibrator kit; other systems either replace the entire computer with a reprogrammed unit or just the computer's chip.


Art Carr Performance Products,

B&M Racing,

Hughes Performance,

JET Performance,

J.W. Performance Transmissions,

Level 10,

Shift Enhancements for Your Automatic, shift point recalibrators
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