Automatic Gearboxes - Functions?

Question

On an automatic gearbox, what do the terms stand for.

P -

R -

N -

D -

S -

'D' is drive, 'R' is reverse, but what are the rest?

Answer 1

Park

Reverse

Neutral

Drive

S(port)? i have no idea what S would be

Answer 2

"P" is park.  "N" is neutral.  Both of these disengage the engine from the wheels entirely, the difference is that "P" has a locking mechanism that will help keep the car from rolling away.

Everything below "D" puts your engine in a lower gear.  These are for descending long hills. On a downhill, your car will accelerate all by itself and you need to slow it down.  You can step on the brake pedal for awhile, but brakes aren't perfect and soon you will overheat the brakes and then you'll have NO brakes!   That's where these lower gears come in.  Shifting down into them forces the engine to spin faster, which makes more heat in the engine - which your engine can do all day  because it has that nice big radiator to cool it :)  The lower you shift, the more engine brakes you get.  But there are only 3 or 4 gears, so your brake selection is very rough, you don't get a lot of choice.  If engine braking isn't enough, you need to use the regular brakes (briefly) to slow down to where it is enough.

Some people think it's also cool to use those lower gears on slippery road conditions, but I'm not one of them and I grew up in the midwest, driving a sportscar in the winter.

Normally you use the first gear past "N".  It's not always called "D".

Answer 3

Park (P) – This selection mechanically locks the transmission, restricting the car from moving in any direction. A parking pawl prevents the transmission, and therefore the vehicle, from moving (although the vehicle's non-drive wheels may still spin freely). For this reason, it is recommended to use the hand brake (or parking brake) because this actually locks the (in most cases, rear) wheels and prevents them from moving. This also increases the life of the transmission and the park pin mechanism, because when parking on an incline with the transmission in park without the parking brake engaged will cause undue stress on the parking pin. An efficiently-adjusted hand brake should also prevent the car from moving if a worn selector accidentally drops into Reverse gear during early morning fast-idle engine warmups.

A car should be allowed to come to a complete stop before setting the transmission into park to prevent damage. Usually, PARK is one of only two selections in which the car's engine can be started. In some cars (notably those sold in the US), the driver must have the footbrake applied before the transmission can be taken out of park. The Park position is omitted on buses/coaches with automatic transmission, which must be placed in neutral with the parking brakes set.

Reverse (R) – This puts the car into the reverse gear, giving the ability for the car to drive backwards. In order for the driver to select reverse they must come to a complete stop, push the shift lock button in (or pull the shift lever forward in the case of a column shifter) and select reverse. Not coming to a complete stop can cause severe damage to the transmission. Many modern automatic gearboxes have a safety mechanism in place, which does to some extent prevent (but doesn't completely avoid) inadvertently putting the car in reverse when the vehicle is moving. This mechanism usually consists of a solenoid- controlled physical barrier on either side of the Reverse position, which is electronically engaged by a switch on the brake pedal. Therefore, the brake pedal needs to be depressed in order to allow the selection of reverse. Some electronic transmissions prevent or delay engagement of reverse gear altogether while the car is moving.

Neutral/No gear (N)– This disconnects the transmission from the wheels so the car can move freely under its own weight. This is the only other selection in which the car can be started.

Drive (D)– This allows the car to move forward and accelerate through its range of gears. The number of gears a transmission has depends on the model, but they can commonly range from 3, 4 (the most common), 5, 6 (found in VW/Audi Direct Shift Gearbox), 7 (found in Mercedes 7G gearbox, BMW M5 and VW/Audi Direct Shift Gearbox) and 8 in the newer models of Lexus cars. Some cars when put into D will automatically lock the doors or turn on the Daytime Running Lamps.

OverDrive ([D], OD, or a boxed D) - This mode is used in some transmissions, to allow early Computer Controlled Transmissions to engage the Automatic Overdrive. In these transmissions, Drive (D) locks the Automatic Overdrive off, but is identical otherwise. OD (Overdrive) in these cars is engaged under steady speeds or low acceleration at approximately 35-45 mph (approx. 72 km/h). Under hard acceleration or below 35-45 mph, the transmission will automatically downshift. Vehicles with this option should be driven in this mode unless circumstances require a lower gear.

Second (2 or S) – This mode limits the transmission to the first two gears, or more commonly locks the transmission in second gear. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time. Some vehicles will automatically upshift out of 2nd gear in this mode if a certain rpm range is reached, to prevent engine damage.

First (1 or L) – This mode locks the transmission in first gear only. It will not accelerate through any gear range. This, like second, can be used during the winter season, or towing.

As well as the above modes there are also other modes, dependent on the manufacturer and model. Some examples include;

    * D5 – In Hondas and Acuras equipped with 5-speed automatic transmissions, this mode is used commonly for highway use (as stated in the manual), and uses all 5 forward gears.

    * D4 – This mode is also found in Honda and Acura 4 or 5-speed automatics and only uses the first 4 gears. According to the manual, it is used for stop & go traffic, such as city driving.

    * D3 – This mode is found in Honda and Acura 4-speed automatics and only uses the first 3 gears. According to the manual, it is used for stop & go traffic, such as city driving. This mode is also found in Honda and Acura 5-speed automatics.

    * + − and M – This is the manual selection of gears for automatics, such as Porsche's Tiptronic. This feature can also be found in Chrysler and General Motors products such as the Dodge Magnum and Pontiac G6. The driver can shift up and down at will, like a semi-automatic transmission. This mode may be engaged either through a selector/position or by actually changing gear (e.g. tipping the gear-down paddle).

Answer 4

p=park

r=reverse

n=nuetral

d=drive

s=second