P R N D 3 2 1…What do those numbers mean

As I headed down a steep hill today, I could feel my van picking up speed, so I instinctively reached up and pulled the shifter down two clicks into “2”.  The engine whirred up, and I was able to ease off the brakes a little.  As a long-time manual transmission driver, I thought to myself how many people who have automatics have ever used the low gear settings on their automatics, or if they even knew when to use them?

I have heard numerous incorrect thoughts as to when to use the numbered gears on the automatic transmission.  Here’s some that I have heard:

“You use them when the engine is having trouble, and you want to reduce the power it puts out”

“A mechanic uses them to troubleshoot the transmission”

” You use them if you are racing the vehicle” (the owner of a Plymouth Mini-van!)

Okay, so I will use this article to enlighten you on when to use these settings in your automatic transmission to improve the safety and performance of our vehicle.

– In mountainous and hilly terrain:  An automatic transmission will automatically go into the highest gear it can because well, it’s an automatic transmission!  The problem is if you are ascending a hill,  the engine will  be turning too slow to pull the vehicle up the hill.  The transmission will sometimes even “hunt” between gears as it attempts to figure out how to handle the increased load.  If you click the shifter down to “3” or even “2” on steep grades, the engine will spin faster, so your car will go up the hill easier with less strain.  When you get to the top though, don’t put it back into “D”, leave it in that low gear for the downhill descent.  When you release the gas pedal, your engine will now put drag on your car’s speed.  This allows you to reduce the amount of pressure needed on the brakes, and thus keeping your brakes from overheating on a long downhill run.

-snow, ice, sand, gravel and other poor traction conditions:  The “2” position is good for these situations.  Part of the job of a transmission is to multiply the torque, or twisting force of the engine so it can get the car moving quickly.  The problem is if your car is sitting on a surface that is a bit loose and slippery, all that twisting force can spin the tires right off the surface.  By selecting “2”, the transmission will not be multiplying the torque as much, and gives you a better chance of pulling away without digging yourself a hole.

-When towing a trailer: Towing requires additional power out of your vehicle, so you will want to place your transmission in a lower gear.  This also reduces the amount of heat buildup in the automatic transmission as well.

Lastly, I want to mention the park position.  The vast majority of drivers when parking their vehicles place the shifter in “P” but do not set the parking brake.  This is fine as long as you have the vehicle sitting on flat land, but if it is on a hill, you are inviting trouble not setting the brake.  This is because automatic transmissions hold the vehicle in one place by one of two methods,  Most place a pawl or peg into one of the gears to keep it from rotating, while other simply bind two gears that are spinning in opposite directions together.  Either way, it means that the weight of the vehicle is being placed on the expensive gears of the transmission.  This is also why when you place the vehicle in gear when it’s sitting on a hill, you get the huge clunk or bang out of the transmission.  For the sake of ruining an expensive transmission, set your brake when on a hill!

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s