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Discussion Starter · #1 ·
I wanted to throw this one out there to those in the know. Does it do any harm to my AT when I shift into N when I crest a big hill and coast down the other side, then shift back into D at the bottom when I need to use the gas pedal again? I do this sometimes when getting off a freeway ramp as well.

My concern is if there is any damage that I may be doing by shifting from N to D or vice versa while in motion?

Thanks
 

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No, but you won't be saving any gas either. The computer will recognize that you are at speed and anticipate you putting it back in to gear by keeping the RPM's where they would have been if you left it in gear. Maybe even slightly higher.

It's also not good for the valve body, but won't do any major damage for at least 30-40k miles.

In short, don't do it. Not worth it.
 

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Discussion Starter · #3 ·
No, but you won't be saving any gas either. The computer will recognize that you are at speed and anticipate you putting it back in to gear by keeping the RPM's where they would have been if you left it in gear. Maybe even slightly higher.

This is incorrect. RPM's drop right down to idle speed. Try it and you will see.

It's also not good for the valve body, but won't do any major damage for at least 30-40k miles.

What will it do to the valve body and why? Not being a smartass, trying to learn.

In short, don't do it. Not worth it.
Thanks for your response. :wavey:
 

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You're not going to really save anything. Keep it in D and maintain control of your vehicle. I don't see any damage at all to your trans. but it's like putting a band aide on a broken arm. You're only going to get a certain amount of mpg. As you already know, these are not the vehicles to save gas. There are better choices out there for that, but not as much fun or capability. Put it in D and go and your best savings will be as easy as possible on the peddle and slower speeds if that's what you're looking for.
 

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Thanks for your response. :wavey:
If your RPM's do in fact drop when put in neutral that is even worse for the transmission. It induces clutch wear every time you drop it back in to gear. The valve body solenoids also take a beating every time that happens. They need to quickly adjust pressures to match transmission rotational speed with engine RPM's. It might feel smooth going from neutral to drive, but a lot is going on when that happens.

Like I said. Can you do it? Yes. Will it save you fuel? Probably not. Is it going to wear out your transmission prematurely? Yes.
 

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A better explanation is this: When you're still in D and let off the throttle you won't be expending much more fuel than if you were at idle. The ECU is going to supply the motor just enough air and fuel to keep it running. Since it is not sensing any throttle input it gives it enough gas to stay running. RPM's don't really matter too much. It's under load via the throttle that causes more air/fuel to be given to the motor. So, what kik said it right. Put it in D and drive it.
 

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Discussion Starter · #7 ·
If your RPM's do in fact drop when put in neutral that is even worse for the transmission. It induces clutch wear every time you drop it back in to gear. The valve body solenoids also take a beating every time that happens. They need to quickly adjust pressures to match transmission rotational speed with engine RPM's. It might feel smooth going from neutral to drive, but a lot is going on when that happens.

Like I said. Can you do it? Yes. Will it save you fuel? Probably not. Is it going to wear out your transmission prematurely? Yes.
This is what I was looking for, Thanks!

I have a pretty short commute and MPG's were not even a consideration when I got my Jeep. I think it may still be some left over instinct from double clutching my old WRX. The thought I may be doing damage will certainly help me break this habit.
 

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What about putting it in Neutral at stop lights?
It's an A-U-T-O-M-A-T-I-C transmission. Leave it in drive. If you want to shift gears get a manual.
 

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It's an A-U-T-O-M-A-T-I-C transmission. Leave it in drive. If you want to shift gears get a manual.
:appl: Thanks for pointing that out. Anyways, there's nothing wrong with wanting to save a little gas, it has nothing to do with wanting to shift gears. Also, when people state, "If you wanted better fuel economy, you shouldn't have bought a Jeep," is ridiculous. If there was a comparable vehicle to the Wrangler that was fuel efficient, many would buy it. But ,there isn't, so some people are interested in methods or mods that may improve fuel economy so they can have their cake and eat it, too. Thanks for listening!!! :dance:

On another note, what part of NJ are you from? I'm not from there, but I met my wife off of Exit 7.
 

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It is also very illegal. Although hard to detect if a cop determines you are doing it you will get a ticket.
If it is, I believe it may depend on your state. I just browsed the NC (where I currently live) statutes and Driver's handbook, and it does not mention it. If it does, it is well hidden in the legal jargon.

Refs:
North Carolina General Assembly - General Statutes - Chapter 20: Motor Vehicles.

http://www.ncdot.gov/download/dmv/handbooks_NCDL_English.pdf

http://www.nclamp.gov/2008%20CLE/Traffic%20Laws.pdf
 

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although the amount of wear on the clutch packs and piston lip seals may be very small and almost imeasurable, just like a standard with a dry clutch every slip in and out will contribute wear over time, and the gas savings or even a set of brake pads are still cheaper than a trans rebuild so better off to leave in gear
 

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:appl: Thanks for pointing that out. Anyways, there's nothing wrong with wanting to save a little gas, it has nothing to do with wanting to shift gears. Also, when people state, "If you wanted better fuel economy, you shouldn't have bought a Jeep," is ridiculous. If there was a comparable vehicle to the Wrangler that was fuel efficient, many would buy it. But ,there isn't, so some people are interested in methods or mods that may improve fuel economy so they can have their cake and eat it, too. Thanks for listening!!! :dance:
Any savings from such practices is neglible. Improving driving habits will yeild far better results.

On another note, what part of NJ are you from? I'm not from there, but I met my wife off of Exit 7.
:eek:

Much like A-Rod in a crucial situation, I'm going to take that 3-0 fastball down the middle without swinging. I'm from much farther north.
 

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gotta agree with most of the guys here. gas savings wouldn't be that significant. i too thought it was frowned upon by LEO's.....something about maintaining control of the vehicle.

cass
 

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I totally agree that improving driving habits is the best thing that can be done, but greater fuel savings result from a combination of practices, such as:

Driving Habits
Regular Maint.
Correct Tire Pressure
EtC, Etc...

Getting the best mileage will not result from just one alone. A lot of little things add up. I'm not saying that putting your vehicle in neutral at a stop is good for the vehicle, but I haven't found any evidence that it is bad. Also, I haven't found any law in MY state, at least, stating it is illegal at stop lights.

Later,
Dave
 
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