switch to neutral, Good habit ?

[eddywei]

hi,
general question.
is it a good habit switching automatic transmission to neutral when you
stop in red light or something needs to wait for a while ?

it is good for the transmission ?
thanks

Eddy

[fredjacksonsan]

It changes where the wear occurs in the transmission. With drive engaged, you'll wear the portion that allows slippage (bands in rwd). Using neutral will wear the engagement portion of the trans. Also depends on the time @ the light. If it's short I'll leave it in, longer will be neutral or even park.

[MagicRat]

Originally Posted by fredjacksonsan

It changes where the wear occurs in the transmission. With drive engaged, you'll wear the portion that allows slippage (bands in rwd). Using neutral will wear the engagement portion of the trans. Also depends on the time @ the light. If it's short I'll leave it in, longer will be neutral or even park.

I respectfully diagree with the technical explaination, although your 'time at the light' advice is good.
Slippage in a properly functioning trans does not occur in the bands or clutch packs. They only slip and wear (slightly) when the transmission actually shifts gear. When stopped and the trans in 'drive' the trans is in first gear, and not moving, with no wear. All the slippage is occuring in the torque converter. The converter is designed to slip, so letting it slip does no harm.

The issue is heat. As the converter allows slipping, it is heating up the fluid, not much, but a bit. Shifting into neutral disconnects the converter so it is not slipping and not building heat in the trans.
However, as soon as you drop it into drive, you will put wear in that first gear clutch pack. This is not a problem either, as that first gear is good for many hundreds of thousands of shifts.

Generally, I will use neutral if stopped for a long time on a really hot day, or if I'm towing a trailer. Otherwise, I leave it in drive.

[fredjacksonsan]

Thanks Rat, I think that's what I was trying to say. This cold is kicking my butt.

[BeEfCaKe]

How about when going at high speeds, and switching to neutral to coast? Will that cause any harm? I didin't think so, but someone has told me it does..

[INF3RN0666]

I THINK it does cause harm but only under certain conditions. I am somewhat making this up as I go along but it's from experience.

When you're coasting at, let's say, 80Km/h (45 M/h) and you decide to shift into neutral so that the car doesn't slow down to the engine's rotational resistance. Well, that'll be fine as long as you don't shift it back into drive. You must come to a stop to shift it back into drive. That's because the engine revs at idle RPM when it's in neutral. If you shift it into drive while going 80 but the RPM is at 750, then you're gonna feel a CLUNK in your transmission or some other unpleasant feeling coming from the car's engine or transmission.

However, if you have an RPM gauge, you can add gas to rev the engine to the proper RPM that is suitable for the speed you are driving at.
For example, driving at 80km/h in my car, my gauge reads an RPM of 1500. So if I was coasting in neutral at 80, i'd rev the engine to 1500 before putting it in drive. It shifts smoothly into that gear and everything is normal.

I hope that helped clear some things up and stops you from experimenting such shifting at highspeeds. Only do it if you have an RPM gauge (I forget the name for those :S ).

One more thing, my car (Eagle Vision ESi) took a couple of those bad shifts when i was going 100, and i didn't rev the engine to speed. My friend's car couldn't take more than 3 of those and he had to rebuild his transmission (Hundai Accent). However, that transmission failure could have been due to his horrible driving and rapid acceleration on a small engine.

[timberdoodle]

I would say that it doesnt really hurt the tranny as long as you arent giving it lots of gas to bring the rpms up and throw it in drive. The transition from neutral idle to drive rpms is very small, and the converter is a fluid clutch allowing all the slippage required to keep the tranny from burning a gear like in a standard. You will notice a little buck because when you put it back in drive you will be slowing the car down with the engine rotation speed.

[Rufe]

I had to cringe a bit when I read this, and want to respond.

If you are reading this thread, and get the idea it is ok to take your
automatic out of gear at highway and above speeds, DON'T.

Why, my opinion as follows:

1. you are losing (throttle) control of your car's handling.
2. There are several automatics with poor gate control, and if you
go over a bump, you can very easily shift into reverse. What do you
think will happen to your transmission then?
3. as stated above, if you shift back into gear at extreme rpms
you will put more stress on the trans, and drive line, in that one episode, than you are trying to save in 20,000 miles (arbitrary number to stress the piont).

[timberdoodle]

Originally Posted by timberdoodle

I would say that it doesnt really hurt the tranny as long as you arent giving it lots of gas to bring the rpms up and throw it in drive. The transition from neutral idle to drive rpms is very small, and the converter is a fluid clutch allowing all the slippage required to keep the tranny from burning a gear like in a standard. You will notice a little buck because when you put it back in drive you will be slowing the car down with the engine rotation speed.

well im not sure what the purpose of shifting into neutral on the highway would be anyways? but if you were to do that, it is not a great idea because yes you can slip and accidentally throw it into reverse, possibly destroying your transmission instantly. As far as loosing throttle control, thats a matter of intelligence really. For the ORIGINAL post, (using neutral at a long stoplight, or maybe a road construction site where you need to sit and wait, it is perfectly fine. THere is not really any advantage over it, but you wont need to keep your foot on the gas is the only benefit. Putting the vehicle in park is probably a better idea, but at a red light, might not be able to shift into drive and go before people start beeping!