YACT: Does moving an auto transmission from drive to neutral create much wear?

[Sukhoi]

Am I introducing significant wear into the transmission by shifting into neutral when coasting to long traffic lights and sitting at long lights?

 

[thedarkwolf]

A little. Why the hell are you doing that anyway? If you think you are saving gas you aren't.

 

[amdskip]

You don't want to coast, free wheeling is not a good thing. You want the motor to slow you down. I would put it in neutral if you are sitting there for 1 minute plus otherwise don't worry about it.

 

[funkymatt]

what amd skip said.. but if there is any wear, it's going to be on your clutch.

 

[thedarkwolf]

He is driving an AUTO there is no reason to put in in neutral period

 

[rahvin]

Originally posted by: thedarkwolf
A little. Why the hell are you doing that anyway? If you think you are saving gas you aren't.

Do you even have any idea how the gearing works in an automatic transmission?

Unlike a manual transmission there aren't really syncromesh gears that recieve wear. All the gears are constantly rotating so there should be almost no wear of any kind when switching gears. This is also true of a manual transmission though if you know what you are doing, in fact a good manual driver can switch gears without using the clutch and without grinding the gears.

 

[funkymatt]

LOL didnt even see that.

yeah, you shouldnt shift into neutral unless you're pushing your car.

 

[treemonkey]

Originally posted by: rahvin

Originally posted by: thedarkwolf
A little. Why the hell are you doing that anyway? If you think you are saving gas you aren't.

Do you even have any idea how the gearing works in an automatic transmission?

Unlike a manual transmission there aren't really syncromesh gears that recieve wear. All the gears are constantly rotating so there should be almost no wear of any kind when switching gears. This is also true of a manual transmission though if you know what you are doing, in fact a good manual driver can switch gears without using the clutch and without grinding the gears.

Change gears on a manual without using the clutch?

 

[funkymatt]

Originally posted by: treemonkey

Originally posted by: rahvin

Originally posted by: thedarkwolf
A little. Why the hell are you doing that anyway? If you think you are saving gas you aren't.

Do you even have any idea how the gearing works in an automatic transmission?

Unlike a manual transmission there aren't really syncromesh gears that recieve wear. All the gears are constantly rotating so there should be almost no wear of any kind when switching gears. This is also true of a manual transmission though if you know what you are doing, in fact a good manual driver can switch gears without using the clutch and without grinding the gears.

Change gears on a manual without using the clutch?[/q]

if you time it correctly, you can over rev the current gear you're in and pop it into the next gear. you need a clutch to initally get it in gear though. did this a couple times in the final days of my VW.

 

[BD2003]

Final days eh?

Oh and I do it all the time. Putting it into neutral on the atx effectively disconnects the torque converter, and will coast a long longer that way. From what Ive read, as long as you dont pop it back into drive at over idle speed, you should be fine.

 

[rahvin]

Originally posted by: treemonkey
Change gears on a manual without using the clutch?

Yes, you have to know the car very well but if the RPM is just right you can change gears without the clutch because the gears are moving at the same speed and will mesh perfectly. The clutch is needed because you often change gears when the gears are moving at different speeds and one gear has to speed up or slow down to mesh with the other gear. When you shift gears from one to the other, such as shifting down you will note the RPM's change, if you rev or coast to that RPM before shifting then you can shift without the clutch.

 

[funkymatt]

i say final days because not long after that the brakes went out while i was driving. not so much fun when in a canyon at 11pm. i made it home in record time though :laugh:

 

[Eli]

I'm curious as well.. My dad has a habbit of putting it in neutral while sitting at a stop light.

 

[Mark R]

It's best never to take the car out of gear while moving for safety reasons - with the car in neutral, you have only limited control. This is equally true in manual as well as auto. When I took my driving test, coasting (in a MT car) was classed as a dangerous mistake and would result in an immediate fail.

There may also be mechanical reasons for not coasting in N - most modern auto boxes use only 'front' oil pumps for lubrication and hydraulics (the pumps are powered by the engine). This means that a decent engine speed is required to get proper lubrication to all the components of the transmission. In neutral with the engine at idle there may not be enough lubrication to ensure correct operation while moving.

Certainly, you should never tow an AT car with the engine switched off unless the driven wheels are off the ground, because without the engine powered lubrication pump running the transmission will wear out very quickly. (Very short distance towing at a very low speed may be acceptable in an emergency)

To see why there is opportunity for wear changing from alternately from N to D requires a little knowledge of how an AT works. However, it is worth remembering that the change from N to D will occur at idle, so is generally a very low stress operation.

The first part of an AT is the torque converter - it goes between engine and gear box and allows the gearbox to turn at a different speed to the engine - basically the engine drives an oil pump, the oil then turns a turbine connected to the GB.

When drive is selected the the gears in the GB are engaged - so the input must turn at a speed related to the road speed of the car. If the car is stopped the input to the gearbox must also be stopped. This means that when the car is stopped, the only moving part in an AT is the engine side of the torque converter (and the lubrication and hydraulic pumps).

When the transmission is in neutral - the GB is disengaged, so the input shaft will spin at the speed of the engine regardless of the road speed of the car.

When you engage drive, appropriate clutches and brakes are activated to select 1st gear. As these engage they will act against the spinning input shaft, and will have to bring it to a stop as the gear engages. There is therefore a small amount of wear on the friction materials. It's only likely to be very little - probably less than a normal gear shift while driving.

In general the safety benefits of having the car out of gear at a junction probably outweight the tiny amount of wear that it could cause.

 

[Sukhoi]

Thank you, that was exactly what I was looking for.