With an AT, is it better to shift into neutral at a light, or use the brake to stop the forward push of Drive?

 

that depends on what you are trying to do.

By shifting, you can let the engine idle instead of running at a higher rpm, thereby conserving some gas. But, each time you shift... you put more wear and tear on the transmission.

either way you cut it... the effect is pretty minimal and would take a LONG time to see any significant results.

being in-gear helps on the occasion that the light changes a little sooner than you expected and now you don't have to fumble to get in gear and have the idiot behind you honking at you for being a split second "slow."

 

I would recommend keeping the car in drive and use the brake to stop it. There is no reason to place an AT into neutral while driving and nothing to be gained by doing so.

 

I'm thinking about being stopped at a light. When the brake isn't depressed, the car moves forward because of "Drive". So, when the brake IS depressed, is the engine fighting against the brake? I'm not worried about brake life, but rather engine/transmission life.

 

There's a torque converter in ATs, one side connects to the engine, the other goes to the transmission. Think of two fans face to face with each other surrounded by liquid. The spinning of one eventually causes the other to spin. So, while some of the force from the engine is getting through to the transmission, most is spinning away in the TC.

Again, shifting out isn't going to give you any noticeable benefit on the transmission wear.

 

Like Goobz says - the AutoTranny is designed to work that way. Simply keep your foot on the brake and release and get on the accelerator when you want to go. All will be good.

 

I've seen people do that - put the AT in neutral while at a stop (light or otherwise). I just try to shut up. In addition to what KC and Goobers already mentioned, it (car in gear/foot on brake) is also a good defensive driving practice. By doing so will also keep you from plowing into the car in front of you in case you get rear-ended or quickly get out of the way if it looks like the car behind you isn't stopping. Of course you'll only notice this if you are mindful of your rear view mirror while at a stop (another defensive driving practice).

Be safe and happy motoring!

 

yes, shift into N is better if you know you are going to a complete stop.

if you're in bumper to bumper and crawling, i think not so good to shift into N to coast and back into D while car is still coasting forward. i feel that lurching when it goes back into gear and it does not feel good.

 

Absolutely not needed and does not benifit you in any way. You may save .001 gallons of gas from the lower idle speed?

More wear on transmission doing this.

If I knew someone did this on a car I was thinking about buying, I wouldn't buy it.

Just saying.

 

Why would it be better???

 

isn't the engine using more gas to keep the car idle if you pop it into neutral rather than using the momentum of the drive train to turn the motor when slowing down while in gear?

i've always thought it was kind of a poseur move personally. the only time i did this was when i had an automatic car that needed new engine and transmission mounts. it would rattle at idle when stopped and shake my watch on my skinny wrist. LOL

 

In at least some states it's illegal to shift into neutral while driving an AT. So on the off-chance something happens, even if it's not your fault, you may be the one getting cited. Good luck explaining "I know I'm the one who got the ticket, but it wasn't my fault" to your ins. co.

 

why would it not be better? less tranny heat, saves a tiny bit of fuel , dont need to worry about creeping into the car in front (gotten hit a few times in the parking lot due to idiots creeping into my rear bumper while they were talking on the phone or looking for something inside the car).

 

Ah, used to be the norm when drivers paid attention when driving...

 

the first one was like over 20yrs ago when normal folks didn't have celphones. hahaha...

 

Amusing and sad... some call it progress... Don't know man... spell check used to be a skill too and not an app.

Long live Forrest Gump!

 

The only time I ever considered shifting an AT to neutral at a stop light was in an old F-150 I wrestled with years ago. It had a high rev at idle issue and really didn't enjoy coming to a stop. Full braking was required to keep it under rein. Problem there was shifting into neutral or park ran it up... then going into drive would shake the rusty loose bits out from under.

Being in gear was one of the ways to control idle speed. Given its own it would reach 35mph at idle in drive with foot off the gas.

Oh those were the days!!!

That beast was part of Ford's first attempt at electronic ignition, HA!

At highway speed the beast would cut the engine. My first inclination was to feather the throttle to get the gas into the cylinders, thinking it was a fuel delivery issue. Then what would happen would be a tremendous exhaust explosion that occurred when the electronics kicked back in. all that gas in the loaded up exhaust stream exploded accompanied by a blast of flame and exhaust smoke and a furthering dislodging of all sorts of rust bits.

Trick was to keep it in gear and the foot off the gas and allow it to 'kick in' on its own. If it didn't the right shoulder became refuge, but you needed to then shift into neutral and wrestle not having power steering and over sized raised white letter sidewalls. Then, it might take 20mins to get things going again...

Glad those days are well behind, but it's fun telling the story.

 

There's no benefit.

The talk about the car saving fuel by it being in neutral versus slowing down with the transmission in drive might not be accurate.

I may be wrong since I'm not an engineer, but from my understanding, when the engine is slowing down but the transmission is engaged (meaning not in neutral), the car goes into closed loop mode (as long as your rpms are within that mode's limits) and there is a deceleration fuel cut, which is why the engine slows down the way it does with your foot off the throttle but also without applying brakes. Theoretically, your car is getting maximum mpg, which is why in cars with digital readouts of instantaneous mpg, it goes to 99.9 (if measured in numbers) or to the maximum amount (if there is a bar graph of some sort) when you are driving and left off of the throttle.

Basically, the engine is just slowing down on its own without fuel being injected since there is no throttle input and it's probably at an rpm well above idle and isn't risking stalling. But if you slow down and shift the transmission into neutral, the rpms drop down all the way to idle, and the ECU will make fuel be injected to keep the engine spinning at idle so it doesn't stall. The difference is minimal if you're only considering doing this when coming to a stop, but if I'm thinking correctly, the difference is not in favor of going into neutral.

If someone can verify that what I said is wrong, feel free to chime in and correct me. That's just my understanding.

 

i'm thinking what you're thinking. it certainly works that way for MT cars, i'm sure it's probably the same with AT.

 

Deeez - you on the mark. This is what I've learned: https://www.fitfreak.net/forums/eco-...f-control.html

+reps to you!

K_C_