what does Over Drive do? whats the diffrence between drive and over drive?

 

http://en.wikipedia.org/wiki/Overdrive_%28mechanics%29

 

Assuming you're asking about automatics,our 4L60Es' have 4 gear ratios,

not including torque convertor 'slippage/stall/efficiency
-1st,3.06:1 ratio-engine turns 3.06 times to provide 1 output turn to the driveshaft
-2nd,1.62:1 ratio-engine turns 1.62 times to provide 1 output turn to the driveshaft
-3rd (D),1:1 ratio-every engine rotation results in 1 driveshaft rotation
-4th (OD), .70:1 ratio,engine has to spin only 7/10 of a rotation to produce 1 driveshaft rotation

also torque convertor lockup occurs when torque demand is low enough(computor controlled) to provide a 1:1 ratio thru the convertor.

 

ahh i see i thought drive gave all 4 gears while OD did something more lol
im new to automatics, this is my first auto Z28

If highway racing starting at a 40mph roll, would it be better to keep the car in Drive or Over Drive?

 

Drive (D) limits you to 1st,2nd, & 3rd (D).
Overdrive (OD) gives you access to all 4 gears.

Torque convertor 'lock-up' can occur in either D or OD when low torque demand occurs.

 

Its better to buy a manual.

BUT to answer your question, I always leave it on O/D incase the race does not stop at 1/4 mile. I have had some highway races where no one wanted to give it up. You do not want to manual shift @ 5k+ rpms.

 

I wouldn't want my trans to shift into OD at WOT.

 

Well, at least not a 4l60.