Ihave lancer 1993 Engine 16V DOHC I want to learn about o/d button what this button do exactly and when Ihave to use it
second : A/T mode what this button do and when Ihave to use it
when I press A/T mode button led (hold ) on in driving panel please reply me
sorry about bad english

think of overdrive as your cruise gear or your final gear.

Leave it on when you driving normal.

Turn it off when you are driving up a steep hill that has lots of curves or where your on and off the throttle and the car keeps on shifting and shifting.

Turning the O/D off will save the transmission as it will not up shift into O/D and then back down.

what about A/T mode (hold)
Idon't understand alot about O/D button pleas tell me a much
thanks

Okay, here you go.

When you turn off overdrive, the yellow dash light says "O/D OFF"

Anyway, if that light is off, the car drives normal, starting in 3rd gear, and shifts whenever it finds suitable. If you floor it, the car will downshift to second, and shift at redline to 3rd, and so on.

If you have overdrive off, and the yellow dash light is on, it basically puts the car in the lowest gear it can handle without redlining. Except, you won't notice any difference unless you're going above 45mph, the general point where 3rd gear would start without the throttle floored. The shifting habit still remains the same, and so does the downshifting if you slam on the gas.

with the overdrive off the transmission only uses 3 gears. with the overdrive on the transmission will use all 4

It'll use all 4 with overdrive on, but only if you're topped out in 3rd. Then you have to floor it just to keep a steady speed.

(IMG:style_emoticons/default/laugh.gif) well yea in that situation it will upshift, but thats a safety mechanism so the engine and trans don't explode. when normal people drive though, it will only use 3 gears when the OD mode is off

lol, I knew it, I was at 7k in 3rd gear doing 122.