Corvette Manual Overdrive Feature Comparison

Many questions are always asked about what features and characteristics of the overdrive are normal or not. Problems always arise since people will compare the operation of different years and think something is wrong. This chart was designed to help you see these variations. There were also changes in the amount of side cover switches on the 4 speed section. All 1984 cars had 3 switches (1st, 2nd, and 4th ). 1985 , 1987, and 1988 cars had a 1st gear switch and 1986 cars had NONE.

Item 1984 1985 1986 1987-88
Min. coolant temp.  80c / 176f 60c / 140f 50c / 122f 50c / 122f
1st Gear

No overdrive ever

Accelerating at >20% throttle turns OD off until 4th gear

Overdrive after downshifting while OD is engaged

No overdrive upshift

OD kicks out on acceleration

Accelerating at 8-38% throttle turns on 2 second delay

Overdrive after downshifting while OD is engaged

OD may be engaged with button

OD kicks out on acceleration, if RPM <4000

Accelerating at >60% throttle turns off overdrive in all gears

Overdrive after downshifting while OD is engaged

OD may be engaged with button

OD kicks out on acceleration, if RPM <3000

Accelerating at >60% throttle turns off overdrive until 4th gear.

2nd Gear

OD kicks out at 60% throttle

OD kicks out at 55mph when accelerating

OD stays engaged after downshifts if <20% throttle

No automatic upshift after kick down

No throttle kick down

OD kicks down at 75% throttle if RPM <2300

Button commands upshift if in direct

No automatic upshift after kick down

OD kicks down at 75% throttle if RPM <2500

Button commands upshift if in direct

No automatic upshift after kick down

3rd Gear

OD kicks out at 60% throttle

OD kicks out at 60mph when accelerating

OD stays engaged after downshifts if <20% throttle

No automatic upshift after kick down

No throttle kick down

 OD kicks down at 75% throttle if RPM <2300

Button commands upshift if in direct

No automatic upshift after kick down

OD kicks down at 75% throttle if RPM <2500

Button commands upshift if in direct

No automatic upshift after kick down 

4th Gear 

OD kicks down at 60% throttle

Automatically upshifts after kick down with no delay

OD kicks down at 80% throttle

Automatically upshifts after kick down after 2 seconds at <80% throttle

Auto OD upshift at 110 mph

OD kicks down at 75% throttle if RPM <2300

Automatically upshifts after kick down with no delay

Button commands upshift if in direct

Auto OD upshift at 103mph

OD kicks down at 75% throttle if RPM <2500

Automatically upshifts after kick down with no delay

Button commands upshift if in direct

Auto OD upshift at 103mph

Manual switch or button

On / Off switch

Opens OD circuit

No RPM limit on downshifts

On / Off switch

Input to ECM

No downshifts over 3500 RPM

Momentary contact switch

Input to ECM

No downshifts over 4000 RPM

Turns program On/Off

Program ON when starting

Switching ON commands upshift in any gear and/or turns program on.

Momentary contact switch

Input to ECM

No downshifts over 4100 RPM

Turns program On/Off

Program ON when starting

Switching ON commands upshift in any gear and/or turns program on.


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