Change Gears on a automatic transmisison?

I'm driving an 02 accord and the gear shift has D4, D3, 2, and 1. A friend said they correspond to the gear the transmission is on. He also said that I could control what gear I want (sort of like manual) if i start at 1, then shift to 2 like a manual, and then shift to D3 and D4 when I want a higher gear. Is this true? Is that how auto transmissions work? Also mentioned something about disabling overdrive, but I didn't catch what he said. I wanted to ask here in case this practice can have harmful effects on my car. Thanks!Change Gears on a automatic transmisison?
Yes, in a way anyway. If you put it in 1, it locks in low gear. If you then shift to 2, it goes no higher than 2nd gear until you shift to 3, etc. etc. So it's like a manual.



As to disabling the overdrive (usually a push button on the lever) it's not a good idea. It will keep it from going into the top gear which will give you a bit more power, but also will drop your mileage.Change Gears on a automatic transmisison?
Yes you can manually shift if you want too, it is a bad idea that car manufacturers put that option on automatics, because some people dont know how to use it and blow the auto trans by leaving it in a low gear and over revving it. Just leave the trans in D for drive and the trans will shift it's self.... it shifts by hydraulic pressure....
Shifting an automatic manually is always a little harder on the box than allowing it do what it's designed to do . . . It's designed to shift when the sensors tell it it's time to shift.



The sensors filter all the various data bits through the computer such as foot pressure on the throttle (interpreted from hydraulic pressure), vacuum at the intake manifold, the rpm of the engine and the speed across the ground (mph).



If you shift it manually to extract more performance than it provides at it's pre-sets, you're putting more torque to the various parts involved in the transaction, especially the clutches and bands.



Nissan makes good cars, but are you willing to tempt fate?



Go ahead . . . throw your dice . . .

.
You can shift an automatic manually without fear of ruining your automatic. Some transmissions are now valved so that if you should hang in gear for more than you should, it will up shift anyway regardless if you don't. Just keep it in D3 if you don't want overdrive. An automatic that is manually shifted still has a slight delay when you shift as opposed to a manual transmission shift. You'll find after a while that this becomes a drag and you will end up just keeping it in D4 while you putt around town.
Shifting an automatic by using the gear selector does absolutely no good. you are putting unnessessary wear on all your internal transmission parts. chances are you are over revving the engine which cuts down on the life of it.. Overdrive means your transmission output is actually turning faster than the engine. The only time it goes into overdrive is at highway speeds and is used to get you better gas milage. Unless you are towing a load overdrive is great. If you accelerate the trans comes out of overdrive.Dont listen to your friend dont try and modify your car it will shorten the life of it.