How do you drive an automatic?

How do you drive an automatic?

Author
Discussion

MitchT

Original Poster:

15,787 posts

208 months

Saturday 25th June 2022
quotequote all
Stupid question, I know. Obviously you put in in "D" and press the accelerator to go and the brake to stop.

However, I have never driven an auto and was wondering about a few of the more subtle elements...

1:
When you park a manual you can leave it in gear to provide more security than the handbrake alone provides. Does putting an auto in "P" effectively do the same thing? Does it lock the car "in gear" making it impossible to move because the engine is off?

2:
If you stop at traffic lights, etc., should you put an auto in "N"? I know with an automated manual with a paddle shift you're recommended to put it in neutral when you're stationary as the clutch will suffer excessive wear if it's in gear. I have no idea what an auto has that equates to a clutch, or if this can be worn excessively by leaving the car in "D" when stopped with the engine running.

3:
Why can't an auto be towed? I once had to be recovered and the breakdown guy on the phone asked if the car was a manual or an auto because autos can't be towed. Why? Surely an auto in "N" is the same as a manual in neutral.

GroundEffect

13,815 posts

155 months

Saturday 25th June 2022
quotequote all
1) P engages the park pawl which locks the system. Stronger than leaving a manual in gear as it's not based on engine compression, it's a physical lock

2) Leave in D. The torque converter is unlocked and you're just creating some heat.

3) mainly due to lubrication or the lack of it. Manual transmissions are splash lubricated by turning the gears/shafts. Auto trans require pump pressure which is generally engine driven pump.

Automatic transmissions are a very different beast to an automated manual or a manual. Don't think of them in that way.

Dodsy

7,172 posts

226 months

Saturday 25th June 2022
quotequote all
1:
When you park a manual you can leave it in gear to provide more security than the handbrake alone provides. Does putting an auto in "P" effectively do the same thing? Does it lock the car "in gear" making it impossible to move because the engine is off?

Park locks up the gearbox but you should use the handbrake as well to reduce load on the locking pin. You’ll always have it in P as you cant remove they keys otherwise.

2:
If you stop at traffic lights, etc., should you put an auto in "N"? I know with an automated manual with a paddle shift you're recommended to put it in neutral when you're stationary as the clutch will suffer excessive wear if it's in gear. I have no idea what an auto has that equates to a clutch, or if this can be worn excessively by leaving the car in "D" when stopped with the engine running.

I leave mine in drive - 250k miles on the clock do must be ok. I put it in neutral if stationary for more than a minute to keep the stress and heat down.

3:
Why can't an auto be towed? I once had to be recovered and the breakdown guy on the phone asked if the car was a manual or an auto because autos can't be towed. Why? Surely an auto in "N" is the same as a manual in neutral.
[/quote]

My Jag is RWD as i understand it the diff oil pump is driven by the prop so towing in N means no lubricant flow in the diff which damages it . No idea about FWD

Edited by Dodsy on Saturday 25th June 14:29

shed driver

2,138 posts

159 months

Saturday 25th June 2022
quotequote all
MitchT said:
3:
Why can't an auto be towed? I once had to be recovered and the breakdown guy on the phone asked if the car was a manual or an auto because autos can't be towed. Why? Surely an auto in "N" is the same as a manual in neutral.
Some autoboxes rely on the engine to be running to provide lubrication to the gearbox. There's dire warnings in the user manual for my ancient rover with a BW 35 auto box. I think it says it can be towed for a matter of a few hundred metres only.

SD.

hersh

351 posts

66 months

Saturday 25th June 2022
quotequote all
MitchT said:
1:
When you park a manual you can leave it in gear to provide more security than the handbrake alone provides. Does putting an auto in "P" effectively do the same thing? Does it lock the car "in gear" making it impossible to move because the engine is off?

2:
If you stop at traffic lights, etc., should you put an auto in "N"? I know with an automated manual with a paddle shift you're recommended to put it in neutral when you're stationary as the clutch will suffer excessive wear if it's in gear. I have no idea what an auto has that equates to a clutch, or if this can be worn excessively by leaving the car in "D" when stopped with the engine running.

3:
Why can't an auto be towed? I once had to be recovered and the breakdown guy on the phone asked if the car was a manual or an auto because autos can't be towed. Why? Surely an auto in "N" is the same as a manual in neutral.
1. You cannot remove the key unless it is in Park. When in Park it locks the drive
2. Automatics have a fluid clutch, totally different from manual clutches, because its fluid it does not wear
3. Complicated answer, if you try to tow it you WILL KILL it.

DonkeyApple

54,919 posts

168 months

Saturday 25th June 2022
quotequote all
A lot of it comes down to good practice. Yes, you can leave an auto in P but it arguably still makes sense to put the hand brake on.

The real benefit to putting an auto in N when in a queue is arguably just to stop blinding the person behind with one's brake lights.

The not towing thing is due to that when in neutral you're disconnecting the gearbox from the engine but not disconnecting the gearbox from the drive train. However, a lot of that is legacy of autos traditionally being almost all RWD. A breakdown can will be lifting the fronts off the road so if you're fwd this issue would be moot.

Evanivitch

19,800 posts

121 months

Saturday 25th June 2022
quotequote all
Non-manual cars are a variety of different beasts these days, with torque converters (sloshing boxes), Dual-clutch transmissions (effectively a robot manual), CVT (voodoo) and electrically driven cars (mostly BEV but some PHEV).

In park, they generally all use a parking pawl, which is a mechanical pin which locks the transmission. It's still worth using the handbrake though, as it's near enough a new box job to replace a pawl on many cars.

Most people will sit on the brake in drive at traffic lights. A torque converter would produce some heat in that situation but really it's not a cause for concern.

MitchT

Original Poster:

15,787 posts

208 months

Saturday 25th June 2022
quotequote all
Thanks all, very helpful.

In terms of "not being able to remove the key if it's not in "P"... I guess that doesn't apply to a car with "keyless go".

aaron-j9c9a

137 posts

35 months

Saturday 25th June 2022
quotequote all
MitchT said:
Stupid question, I know. Obviously you put in in "D" and press the accelerator to go and the brake to stop.

However, I have never driven an auto and was wondering about a few of the more subtle elements...

1:
When you park a manual you can leave it in gear to provide more security than the handbrake alone provides. Does putting an auto in "P" effectively do the same thing? Does it lock the car "in gear" making it impossible to move because the engine is off?

2:
If you stop at traffic lights, etc., should you put an auto in "N"? I know with an automated manual with a paddle shift you're recommended to put it in neutral when you're stationary as the clutch will suffer excessive wear if it's in gear. I have no idea what an auto has that equates to a clutch, or if this can be worn excessively by leaving the car in "D" when stopped with the engine running.

3:
Why can't an auto be towed? I once had to be recovered and the breakdown guy on the phone asked if the car was a manual or an auto because autos can't be towed. Why? Surely an auto in "N" is the same as a manual in neutral.
2. Most cars have the start/stop function and auto hold. That’s what I personally use.

3. I heard it’s something to do with the gearbox. My brother works for the yellow van break down service n he says their computer will tell them if they can tow a car or not

MDL111

6,891 posts

176 months

Saturday 25th June 2022
quotequote all
hersh said:
1. You cannot remove the key unless it is in Park. When in Park it locks the drive
2. Automatics have a fluid clutch, totally different from manual clutches, because its fluid it does not wear
3. Complicated answer, if you try to tow it you WILL KILL it.
I sometimes park my car in N, so on mine you can remove the key even if it is not in P

cuprabob

14,414 posts

213 months

Saturday 25th June 2022
quotequote all
Just be careful the first time you need to do an emergency stop smile

If you are used to a manual, your instinct is to push the brake and clutch at the same time, meaning in the the auto you end up pushing the brake pedal with both feet and stopping rather quickly....so a friend told me smile

LunarOne

5,089 posts

136 months

Saturday 25th June 2022
quotequote all
I bought my first automatic a year ago (1992 BMW 730i), although I drove my mother's automatic 1984 Mercedes 230E after I passed my test for some time before I could afford a car of my own. Anyway I always put them in neutral when I'm going to be stationary for more than a few seconds, if for no other reason than to save fuel. When in drive, the engine is loaded and trying to push the car forward against the brakes, while in neutral the engine is just idling which means it's only using fuel to turn itself.

I'm sure modern automatic gearboxes work differently. I've driven many modern Porsches with PDK and they don't seem to be straining against the brakes when stationary - but then those are more automated manuals than true slushbox transmissions.

Here's what my BMW's manual says:


Edited by LunarOne on Saturday 25th June 14:53

paradigital

843 posts

151 months

Saturday 25th June 2022
quotequote all
MitchT said:
Thanks all, very helpful.

In terms of "not being able to remove the key if it's not in "P"... I guess that doesn't apply to a car with "keyless go".
In my 440i, the gearbox will put itself in park if you press the engine stop button (it will even physically move the gear selector over from manual/tiptronic when parking up).

MitchT

Original Poster:

15,787 posts

208 months

Saturday 25th June 2022
quotequote all
Interesting to know, particularly as it's the 4 Series that I'm interested in and the fact that most for sale seem to be autos has prompted my curiosity.

W201_190e

12,738 posts

212 months

Saturday 25th June 2022
quotequote all
I never used N in any of mine. Usually foot on the brake if only a little while or in park.

Smint

1,686 posts

34 months

Saturday 25th June 2022
quotequote all
Some people don't bother with the park brake when they park an auto, i don't when at home on the flat part of my drive, but always apply the handbrake soldily when parked elsewhere, because if someone nudges your car and its only held on the parking pawl in the auto box they could cause serious damage inside the box, any fix inside an auto box is going to be expensive.

Some automated manual boxes don't have a P parking pawl at all, if you wish to leave the car in gear as well (advisable when parking on an incline), you'll have to engage first or reverse and then switch the engine off with the car still in gear.

For traffic lights etc, i judge how long the stop is likely to be, under a minute i'll leave it in D, longer then drop it into N, no comment on automated manuals however many clutches it boasts, hateful things.

Towing for any distance (ok round the block) has always been inadvisable with auto boxes (some manual truck gearboxes too which relied on pump fed oil in the box), can completely destroy a box...on trucks they remove a hafl shaft before dragging it in, if you have no option but to tow an automatic a long distance then disconnect the propshaft from the box.

Edited by Smint on Saturday 25th June 15:07

Evanivitch

19,800 posts

121 months

Saturday 25th June 2022
quotequote all
cuprabob said:
Just be careful the first time you need to do an emergency stop smile

If you are used to a manual, your instinct is to push the brake and clutch at the same time, meaning in the the auto you end up pushing the brake pedal with both feet and stopping rather quickly....so a friend told me smile
First time you drive an automatic be careful coming to a stop full-stop. People tend to dip the clutch with their left foot and find the brake instead.

First time driving an automatic, tuck your left foot behind your right leg (where safe and practical).

paintman

7,669 posts

189 months

Saturday 25th June 2022
quotequote all
MitchT said:
Thanks all, very helpful.

In terms of "not being able to remove the key if it's not in "P"... I guess that doesn't apply to a car with "keyless go".
Or older cars that don't have an electronic interlock.

Having spent the last 20 odd years doing minor bodywork on cars & needing to move customer's cars there are quite a few different autoboxes out there & if you assume they're all the same then you might have problems.

If you are driving an automatic for the first time ask the owner/seller of the car & if the handbook is present have a quick read through the relevant sections.

My first car was an automatic Mini Clubman estate. 1972.
A young lad from the garage came out to our house with an older mechanic to collect it for service.
Got in, pulled choke fully out & started the car.
Put it in 'R', released the handbrake & put his foot on the accelerator.
Mini took off like a scalded cat & collided rear to rear with my father's Hillman Hunter estate which was parked further along the drive.
Body work involved included two new rear ( as in access to the estate area) doors on the Mini & a new rear bumper & tailgate on the Hunter. All paid for by the garage.
Apparently he'd never driven an auto before & decided he didn't need to bother asking either my father or the other mechanic who'd brought him to collect the car.

VS02

2,003 posts

59 months

Saturday 25th June 2022
quotequote all
If you are looking at a 4 series, they are more akin to a robotised manual gearbox than a traditional automatic.
All non M 4 Series models with an “auto” were/are equipped with an 8 speed dual clutch semi automatic transmission made by ZF. I would say put the car in N at a standstill to avoid wear to the clutch as it isn’t a TC trans, also crawling is not good for the DCT.

VS02

2,003 posts

59 months

Saturday 25th June 2022
quotequote all
Evanivitch said:
cuprabob said:
Just be careful the first time you need to do an emergency stop smile

If you are used to a manual, your instinct is to push the brake and clutch at the same time, meaning in the the auto you end up pushing the brake pedal with both feet and stopping rather quickly....so a friend told me smile
First time you drive an automatic be careful coming to a stop full-stop. People tend to dip the clutch with their left foot and find the brake instead.

First time driving an automatic, tuck your left foot behind your right leg (where safe and practical).
I did this with a 3 and a half tonne fully loaded Sprinter when I was 18 and with 6 months on my licence which was not pleasant. I did it multiple times including at 60mph with someone coming behind me which made many poos come out and angry drivers behind me.

That being said I find it easier to keep the left foot on the footrest and naturally I press my foot in to the footrest rather than the clutch pedal.