Shift blocking is a feature of
automobile
A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...
manual transmission
A manual transmission (MT), also known as manual gearbox, standard transmission (in Canadian English, Canada, British English, the United Kingdom and American English, the United States), or stick shift (in the United States), is a multi-speed ...
s added to improve fuel economy ratings in the
Corporate Average Fuel Economy (CAFE) system by preventing a driver from switching from first gear to second or third as would be done normally. A solenoid prevents the shifter from engaging these gears, forcing the driver to shift from first to fourth gear. The solenoid is computer controlled, and will deactivate if the throttle is opened wide enough, or the car reaches speeds above those typical in city driving.
Usage
The skip shift feature was originally introduced in the
Chevrolet Corvette
The Chevrolet Corvette is a line of American two-door, two-seater sports cars manufactured and marketed by General Motors under the Chevrolet marque since 1953. Throughout eight generations, indicated sequentially as C1 to C8, the Corvette is not ...
in the late 1980s,
with the name CAGS (Computer-Aided Gear Selection), and is present on many sporting cars produced in the US from the 1990s onwards on every car fitted with the
Tremec T-56 and TR-6060, including the
Dodge Viper
The Dodge Viper is a sports car that was manufactured by Dodge (by Street & Racing Technology, SRT for 2013 and 2014), a division of American car manufacturer Chrysler from 1992 until 2017, having taken a brief hiatus in 2007 and from 2011 to 20 ...
,
Pontiac Firebird
The Pontiac Firebird is an American automobile built and produced by Pontiac (automobile), Pontiac from the 1967 to 2002 model years. Designed as a pony car to compete with the Ford Mustang, it was introduced on February 23, 1967, five months a ...
,
2004-2006 Pontiac GTO,
Pontiac G8 GXP, V8/SS
Chevrolet Camaro
The Chevrolet Camaro is a mid-size American automobile manufactured by Chevrolet, classified as a pony car. It first went on sale on September 29, 1966, for the 1967 model year and was designed to compete with the Ford Mustang. The Camaro sha ...
and
Cadillac CTS-V.
Criticism
The effect of the system on normal driving has been described as "dreaded",
"awful"
and "annoying".
In 1994 Popular Science noted that "if something like an oncoming truck makes you change your mind, the car's response is doggedly slow."
Eliminators
Owners manuals for the Corvettes in which it was first implemented contained photographs of the system components "captioned to caution drivers not to disconnect
hewire, or the skip-shift function would no longer function."
These photos, along with the continuing, decades-long ability to bypass the system easily with a simple resistor, make it clear that
GM has never intended to make the system difficult to bypass. If anything, it has been made as simple as possible while still satisfying federal regulations. Skip shift eliminators are produced for quick and simple DIY installation to circumvent the GM CAGS system.
, these were commercially available for about –, or could be made with a little soldering for about .
Notably, neither workaround will eliminate the "1-4 skip shift" dash indicator light, which will continue to operate regardless.
ECU tuning is required to eliminate the dash indicator light.
References
Automotive transmission technologies
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