Shift blocking

Shift blocking is a feature of automobile six-speed manual transmissions 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.

Overview

The skip shift feature was originally introduced in the Chevrolet Corvette in the late 1980s,[1] CAGS, 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 Pontiac Firebird,[2] Dodge Viper,[3] and Cadillac CTS-V.[4] Owners manuals for the Corvettes in which it was first implemented contained photographs showing the system "captioned to caution drivers not to disconnect this wire, or the skip-shift function would no longer function."[1]

Criticism

The effect of the system on normal driving has been described as "dreaded",[2] "awful"[5] and "annoying".[3] In 1994 Popular Science noted that "if something like an oncoming truck makes you change your mind, the car's response is doggedly slow."[6]

Eliminators

Skip shift eliminators are produced for quick and simple DIY installation to circumvent the 'Computer-Aided Gear Selection' GM uses to implement the shift blocking feature.[7] These are commercially available for about $20–40, or can be made with a little soldering for about $7.[4] Notably, neither workaround will eliminate the "1-4 skip shift" dash light, which will continue to operate regardless. ECU tuning is required to eliminate the dash lights function.

References

  1. 1 2 Mike Allen. "6 Clever Ways the Car Industry Has Gamed the CAFE Fuel Economy Standards". Popular Mechanics.
  2. 1 2 Jim Kenzie (27 April 1996), "Firebird burns street Pontiac brings back Ram Air heritage and asphalt-ripping power", Toronto Star, p. H1
  3. 1 2 Arv Voss (4 July 2008). "Dodge Viper SRT10 gets you there in a hurry". Washington Times.
  4. 1 2 Ben Wojdyla (13 May 2005). "How To Disable GM’s Manual Skip Shift For Seven Bucks". Jalopnik.
  5. ↑ Jim Kenzie (16 July 2005), "2006 Chevrolet Corvette", Wheels.ca
  6. ↑ Jim McCraw. Muscle Cars (March 1994 ed.). Popular Science. p. 71.
  7. ↑ Richard Newton (2006). Corvette C5 Performance Projects: 1997-2004. Motorbooks. p. 85. ISBN 0-7603-2081-0.


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