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YACT: A few questions on automatic transmissions

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psteng19

Diamond Member
1. Is it ok to move from N to D while the car is moving? <-- happened a few times by accident (not neutral drop).

2. What is actually happening when you put it in Park (that prevents the car from moving)?

3. Does a lot of unnecessary shifting cause premature wear and tear (i.e. moving from D to R a lot while parallel parking)?
 
You're really better off not changing the transmission from one thing to another at all when the car is moving (unless maybe it is from the different D stages, like from D3 to D4). It isn't necessarily going to blow your transmission if it happens once or twice, but I definitely would be more careful about moving the shifter around while the car is moving.
 
Read somewhere that it isn't recommended that you shift at all while the car is moving... auto tranny at least. I think it was in one of those threads asking if you shift to neutral when you're coasting to a stop.
 
Originally posted by: boyRacer
Read somewhere that it isn't recommended that you shift at all while the car is moving... auto tranny at least. I think it was in one of those threads asking if you shift to neutral when you're coasting to a stop.
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It's not a good idea to shift a manual while the car's moving either, or so i read. 😀
 
Originally posted by: LeRocks
Originally posted by: boyRacer
Read somewhere that it isn't recommended that you shift at all while the car is moving... auto tranny at least. I think it was in one of those threads asking if you shift to neutral when you're coasting to a stop.
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It's not a good idea to shift a manual while the car's moving either, or so i read. 😀
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😛 that's why i said auto tranny... 😀
 
going from neutral into D isn't the worst thing in the world. if you somehow stall it on the road you have to put it in N then back in D while moving.
 
Originally posted by: Spoooon
Will changing gears while moving in an automatic do damage? Say from D to 2?
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geez no offense guys but these questions are absurd. Let's see.. the whole point of a transmission is to *change* gears. Now why on earth would that damage it, when it's designed to do that!

I don't think even going from N to D hurts anything, as long as you're not on the gas when you do it.
 
Originally posted by: Ultima
Originally posted by: Spoooon
Will changing gears while moving in an automatic do damage? Say from D to 2?
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geez no offense guys but these questions are absurd. Let's see.. the whole point of a transmission is to *change* gears. Now why on earth would that damage it, when it's designed to do that!

I don't think even going from N to D hurts anything, as long as you're not on the gas when you do it.
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I didn't think it would do any damage, but some of the posts made me wonder.
 
My feelings on the issue:

From D to N while moving? Fine.

From N to D while moving? Don't make a habit of it, but once by accident won't hurt.

Shifting between the forward gears while moving? That's fine, within reason. The automatic transmission already does this for you, so it is technically not bad. A downshift to 3 (AKA "OD OFF" on some cars) or 2 to prevent you from going too fast down a hill is fine while moving, but don't make a habit of downshifting to slow down at stop signs and such. Downshifts that cause the engine to rev way up suddenly are not a good thing! Use the brakes. That's what they're there for, and they're without exception, a lot cheaper than the transmission.

Shifting from D to R a few times in a row to park is fine, but you should be at a 100% STOP, not still rolling at all, and the engine should be idling at a normal speed every time you shift. Also, make sure you have felt it fully engage (it takes about a second in most cars) before you give any gas to move after reversing direction.

Howard's got the right answer for number 2, but you should still use the brake on a hill or in slippery weather. Why? Say you park on a hill and there's some ice in the gutter. One drive wheel gets parked on ice, and the other gets parked on a dry part of the street. Because of the differential, only one wheel needs to lose traction for the car to roll. Suddenly the car is rolling down a hill, with the wheel on the ice spinning backwards!
 
I thought manually shifting a "regular" automatic is the same as shifting an automatics with "manual override" with buttoms.
 
2. Some square notches on the output of the transmission are engaged so that nothing moves.
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Which brings me to this question.

Why bother with this mechanism?
Why not just leave it in gear? or pop it in neutral and use the handbrake?

Shifting from D to R a few times in a row to park is fine, but you should be at a 100% STOP, not still rolling at all, and the engine should be idling at a normal speed every time you shift. Also, make sure you have felt it fully engage (it takes about a second in most cars) before you give any gas to move after reversing direction.
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I hate it when people think they can go from D to R while the car is still moving in the opposite direction. They're trying to look cool or save time, but do they not know they're killing their trannies?
 
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
 
Wow. You people are over-reacting. Automatic trannies are pretty robust these days.

1. Yes, it is FINE to move from N to D while driving. The gears will synchronize automatically, and it will fall INTO overdrive or 3rd gear so it doesn't matter about car's speed - the gear is so low that the change in speed (from 0 rorations to the rotations from the road) will be pretty small.

2. When you put it in park, the one of the gears goes up against the housing for the transmission and stays there. This is because to leave it in a gear, you would be inable to start it. To leave it in nuetral would depend on the person to use the e-brake, which is a WEAR part - something that is designed to wear down. The gears in the tranny are HUGE, with thousand of small teeth - they wont be stripped easily.

3. Of course. The question is kind of silly. Unecessary shitfing adds unnecessary wear. Shift when necessary, don't when not.

 
Originally posted by: Eli
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
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I'm not sure where you read this, but it's not necesarily true. If you are going from a slow ROLL, it will just restrict the car to that gear. Because the auto uses planetary gearing, going down in gears usually just engages another gear, not necessarily changes gears.
 
Originally posted by: technogeeky
Originally posted by: Eli
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
Click to expand...


I'm not sure where you read this, but it's not necesarily true. If you are going from a slow ROLL, it will just restrict the car to that gear. Because the auto uses planetary gearing, going down in gears usually just engages another gear, not necessarily changes gears.
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Huh? Please come back when you know more about an automatic transmission than "it uses planetary gearing.". 😛

The clutch packs that control which gears are engaged and disengaged.. that is what I'm talking about.
 
Originally posted by: psteng19
2. Some square notches on the output of the transmission are engaged so that nothing moves.
Click to expand...
Which brings me to this question.

Why bother with this mechanism?
Why not just leave it in gear? or pop it in neutral and use the handbrake?

Shifting from D to R a few times in a row to park is fine, but you should be at a 100% STOP, not still rolling at all, and the engine should be idling at a normal speed every time you shift. Also, make sure you have felt it fully engage (it takes about a second in most cars) before you give any gas to move after reversing direction.
Click to expand...
I hate it when people think they can go from D to R while the car is still moving in the opposite direction. They're trying to look cool or save time, but do they not know they're killing their trannies?
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leave it in gear? Because in an automatic tranny, there is no mechanical connection between the drive wheels and the transmission. Automatic trannies use a torque converter which works by hydraulic fluid.. sort of. The specifics can be found at HowStuffWorks.com 🙂
 
Originally posted by: Eli
Originally posted by: technogeeky
Originally posted by: Eli
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
Click to expand...


I'm not sure where you read this, but it's not necesarily true. If you are going from a slow ROLL, it will just restrict the car to that gear. Because the auto uses planetary gearing, going down in gears usually just engages another gear, not necessarily changes gears.
Click to expand...

Huh? Please come back when you know more about an automatic transmission than "it uses planetary gearing.". 😛

The clutch packs that control which gears are engaged and disengaged.. that is what I'm talking about.
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It's not any harder for it than if it shifted by itself. Same thing. Shifting for nothing will add extra, but normal wear and tear. Shifting while under full throttle isn't a very good idea though.
 
Originally posted by: Eli
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
Click to expand...

Eh? If you're in Drive, going say 20MPH, and you floor it, the trans will kick down to 2nd, or possibly 1st. There's no difference if you do it yourself. And if you're over a certain speed, the trans won't kick down (automatically or manually).


Shifting while under full throttle isn't a very good idea though.
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Again, eh? Automatic shifting under full throttle is the same to the trans as shifting manually under full throttle. (unless you're talking about shifting from Neutral to Drive under full throttle!)


JC
 
Originally posted by: JC
Originally posted by: Eli
You aren't supposed to move from D to 1 or 2 while moving, it's very hard on the clutch packs in the transmission.
Click to expand...

Eh? If you're in Drive, going say 20MPH, and you floor it, the trans will kick down to 2nd, or possibly 1st. There's no difference if you do it yourself. And if you're over a certain speed, the trans won't kick down (automatically or manually).


Shifting while under full throttle isn't a very good idea though.
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Again, eh? Automatic shifting under full throttle is the same to the trans as shifting manually under full throttle. (unless you're talking about shifting from Neutral to Drive under full throttle!)


JC
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ummm... if you're going 20 mph, you're probably already in 2nd... it'd probably go down to 1st
 
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