Possibly doing damage to engine/transmission
6th Gear Member
Joined: Feb 2007
Posts: 7,635
From: state of confusion
↑↑↑ Not sure I see that being possible. Sounds more like urban legend.
If it's a MT and you're going fast enough to beat a full-race turtle, you'd have to have an unusually quick shifting hand plus be flat-out lucky to beat the reverse lockout and get the idler gear to mesh with a gear that's turning in the opposite direction. I can picture a scene with lots of grinding, which isn't particularly good for the tranny internals. But not dropping it entirely.
If it's an AT, the 'downshift' direction is away from N and R, and usually there's a thumb button reverse lockout.
Maybe somebody should send this one in to 'Mythbusters'?
Norm
If it's a MT and you're going fast enough to beat a full-race turtle, you'd have to have an unusually quick shifting hand plus be flat-out lucky to beat the reverse lockout and get the idler gear to mesh with a gear that's turning in the opposite direction. I can picture a scene with lots of grinding, which isn't particularly good for the tranny internals. But not dropping it entirely.
If it's an AT, the 'downshift' direction is away from N and R, and usually there's a thumb button reverse lockout.
Maybe somebody should send this one in to 'Mythbusters'?
Norm
Thread Starter
3rd Gear Member
Joined: Aug 2009
Posts: 772
From: Jasper, IN
I did a quick test today about the engine providing just enough fuel to keep it from dying when we are not applying the gas peddle. I have a significant hill near my residence and as I came down it today, I noticed my RPMs were sitting at about 1.75. Even though I wasn't pushing the gas peddle and coasting down the hill at 60mph. I watched the needle for a few moments and it did not change position. As soon as I put the car into N, the RPMs dropped to under 1rpm. This would most definitely save a lot of gas over time. Again I drive an automatic. I don't think putting the car into N while moving is bad. But would putting the car back into D before I came to a stop cause damage. I don't wouldn't appy gas until the car has fully shifted into D.
3rd Gear Member
Joined: Jan 2009
Posts: 924
From: San Jose, California
I think it should just be left into D an unless it was in neutral for a long period of time, its not going to save gas and just putting unneccessary movement on the trans. If going into to neutral would save that much gas then i would be bet autos would have some sort of function that puts it in neutral when applying breaks. So the best thing to do is just keep it in drive
4th Gear Member
Joined: Feb 2010
Posts: 1,532
From: dark side of the moon
If you downshift properly in a manual (waiting until you slow to a proper speed appropriate to the gear you want to shift down into), your revs won't be so high. I always downshift and usually don't have to actually press my brakes until I'm probably less than two car lengths from the stopped vehicle in front of me. And in some instances when traffic is flowing well, I only have to press the brakes to stop me moving the last couple feet and to also flick on the brake lights for the vehicle behind me.
Generally, in the Mustang, when downshifting, I slow the car down to about 2k, then shift down, which puts me back to just under 3k, and repeat for each remaining gear. This way, I'm not at high revs and lower gears. Of course, some instances I have to brake harder or sooner than I can downshift, but then again, you can't always judge how everyone else is driving around you. I firmly believe in having the car in a gear appropriate to the speed I'm travelling to aid in defensive driving. It has helped a few times in the past.
But, to each his own. I know a friend of mine drives stick, and is always sticking it in neutral or mashing down the clutch when coming to a stop, even if we're still travelling at 50mph or something. Though, he does drive a base Honda Fit with a five speed...........................pointless.
Though I'm more accustomed to downshifting because I drive large Mack Trucks (Concrete Pumps to be exact) and it is critical to using downshifting and engine braking to slow those large suckers down. So I've just used that experience to regular vehicles.
Generally, in the Mustang, when downshifting, I slow the car down to about 2k, then shift down, which puts me back to just under 3k, and repeat for each remaining gear. This way, I'm not at high revs and lower gears. Of course, some instances I have to brake harder or sooner than I can downshift, but then again, you can't always judge how everyone else is driving around you. I firmly believe in having the car in a gear appropriate to the speed I'm travelling to aid in defensive driving. It has helped a few times in the past.
But, to each his own. I know a friend of mine drives stick, and is always sticking it in neutral or mashing down the clutch when coming to a stop, even if we're still travelling at 50mph or something. Though, he does drive a base Honda Fit with a five speed...........................pointless.
Though I'm more accustomed to downshifting because I drive large Mack Trucks (Concrete Pumps to be exact) and it is critical to using downshifting and engine braking to slow those large suckers down. So I've just used that experience to regular vehicles.
Thread Starter
3rd Gear Member
Joined: Aug 2009
Posts: 772
From: Jasper, IN
I guess where I have an issue with it is, when you are shifting a MT vehicle, you put the car into N, so to speak, when you push the clutch in to shift. For example, if you are going from 3rd to 4th at about, lets say 40MPH, you first put the car into N, shift and then release the clutch into a gear system that is trying to move at 40MPH. How is that different than putting AT vehicle into N when coasting and when you need to speed up, you put it back into D and let the engine determine which gear to go in. As long as you wait for the car to fully shift into D before applying gas.
1st Gear Member
Joined: Jan 2010
Posts: 132
From: Kentucky
I answered your original question back in reply # 22. How you guys can still be debating this issue is beyond me. If you don't want to here the correct answer to your question then why ask the question in the first place??? You will kill your auto tranny if you let it coast in nuetral. That is the correct answer to your original question.
6th Gear Member
Joined: Feb 2007
Posts: 7,635
From: state of confusion
I guess where I have an issue with it is, when you are shifting a MT vehicle, you put the car into N, so to speak, when you push the clutch in to shift. For example, if you are going from 3rd to 4th at about, lets say 40MPH, you first put the car into N, shift and then release the clutch into a gear system that is trying to move at 40MPH. How is that different than putting AT vehicle into N when coasting and when you need to speed up, you put it back into D and let the engine determine which gear to go in. As long as you wait for the car to fully shift into D before applying gas.
Most current PCM's will cut fuel completely on closed throttle deceleration as long as the rpms are ABOVE a certain level. Seems to me that using zero fuel at 2000 rpm (or whatever, as long as it's above the minimum fuel cut rpm) is still less than a small amount of fuel at idle rpm.
I have an aftermarket multiport EFI system on another car, and it would only take a few minutes for me to turn the injector pulse widths in the fuel map down to zero over any range within the fuel map that you'd care to choose. Want to shut the fuel off for RPM's above 2000 at high manifold vacuum? No problem. Want to see if you can drop that fuel cut low rpm point down to 1700? Gimme another minute or two. And this is with an EFI that uses an "old-fashioned" mechanical throttle, not DBW plus a PCM 'learning' feature with who knows how many lines of computer code.
Norm
5th Gear Member
Joined: Dec 2006
Posts: 4,552
From: Redding, CA
There is absolutely no point in this. For one it's going to just cause faster wear on the brakes by not using engine braking. Also you're not going to cause damage/wear to the trans due to the slippage of the torque converter. It's made to do this.
The same thing applies to people who have a manual and put it in neutral when coming to a stop. Makes no sense at all and is actually dangerous to do that.
Shifting behaviors some people come up with is really strange.
For an auto, really the only time neutral should be used is if you need to push the car. But it's never a good or smart idea to put it in neutral while you're driving. For a manual, the only times it makes sense to go in neutral is when starting (safety) and if you need to jump start it. Any other time, stay the fak out of N!
The same thing applies to people who have a manual and put it in neutral when coming to a stop. Makes no sense at all and is actually dangerous to do that.
Shifting behaviors some people come up with is really strange.
For an auto, really the only time neutral should be used is if you need to push the car. But it's never a good or smart idea to put it in neutral while you're driving. For a manual, the only times it makes sense to go in neutral is when starting (safety) and if you need to jump start it. Any other time, stay the fak out of N!
Engine breaking is very minor compared to what your brakes actually can accomplish.
I see the point about needing to move in an emergency situation. If I'm alone at a stop light and see traffic coming from behind I might put it in gear. Otherwise, I leave it out of gear so that the time it takes to put it in gear and get going let's any of the red light runners make through. It also releaves any pressure on my throw out bearing.
Brakes are cheaper than the throw out bearing, tranny, motor, clutch etc. It's much cheaper and easier to use the brakes for what they are meant for and the engine for what it was meant for.
There are time when engine braking is good or needed. It just shouldn't be everytime you come to a stop or need to slow down.
I would agree that it is fun and I enjoy listening to the motor slow the car.
2nd Gear Member
Joined: Jan 2007
Posts: 458
From: Virginia
OP -> Do as you please, it doesn't matter and it's up to your driving style. I commute 42 miles each way over a mountain with a Grand Prix GT and shift that car in to neutral almost daily at interstate speeds. (Car will maintain 65-72MPH for almost 5 miles in N during one stretch of interstate.) 250,000+ miles can't be wrong!