[Auto Talk] Can regularly shifting to Neutral on an automatic gear damage it?

Adrian Wong · 14th May 2008, 01:08 AM

Hi guys!

I have an automotive-related question for the gearheads in this forum.

My car has a 4-speed automatic transmission and I regularly shift to Neutral whenever I go downhill to let the car coast and save a little petrol.

Of course, engaging the auto transmission after that can sometimes cause the engine to rev up suddenly. So I normally tap the pedal a little to rev the engine before engaging the auto gear.

Someone recently told me that doing so will damage the automatic transmission. Is that true? Thanks!

wiiz · 14th May 2008, 04:00 AM

the lesser you changing gear, the longer your gearbox last.
....and you dont have to put it in N, in D just lift off your pedal it still coasting.

btw...
Howstuffworks "How to Drive Economically: Tips and Guidelines"

zy · 14th May 2008, 05:15 AM

i think this doesnt really apply to modern cars.
modern cars have advanced ECU, they should minimalize fuel compsumtion while you are coasting downhill. besides, while coasting downhill in neutral, your car engine still uses fuel to maintain the rpm even if you are in neutral.

Chai · 14th May 2008, 08:12 AM

I think it's better to leave the gear in D while the car is moving, because you are not using more or less fuel as long as you are not on the pedal.

Unlike manual cars, when your car is engaged to a gear, especially at high engine speed, your car will slow down even on a down hill slope. That's the reason why some like to shift to neutral, but it's dangerous.

PsYkHoTiK · 14th May 2008, 08:56 AM

I wonder how much the torque convertor would like that.

Coasting is bad practice IMO.

Just how much can you save anyways?

Plus coasting in gear may actually save you more gas (foot off throttle, the gas mixture usually cuts back as opposed to idling its still on).

Plus engine braking wont wear out your brakes as much (aka coast in gear).

Coasting in neutral is dangerous...

Adrian Wong · 14th May 2008, 10:28 AM

Actually, coasting in neutral can save a LOT. In city driving, I went from 8.5 km/l to about 10.5 km/l. On the highway, I went from 10 km/l to about 13 km/l.

The thing is I have no idea if it's bad on the transmission.

As for safety, I don't see how it can be a problem because I treat it like a manual shift. In the sense, I can shift out of neutral pretty quick (my hand is always on the shift stick).

PsYkHoTiK · 14th May 2008, 12:49 PM

Coasting in gear with the throttle closed (aka foot off the pedal) closes your fuel injectors (aka not using fuel at all). Most of not all modern fuel injection systems cut off the fuel if not most of it while coasting in gear. However, it is not so when you are in neutral.

Coasting is dangerous as the balance of your car is affected (try cornering with your car in neutral). It is a good reason why they made it illegal in some places. Not to mention in an emergency, you have much less reaction time (now that you have to get back in gear).

As for your tranny, your torque converter will not like you.

Plus with coasting you use up more of your brakes (tranny is a low wear component). I always engine brake when possible (and coast in gear).

Chai · 14th May 2008, 03:02 PM

Very bad for torque converter.

Coasting in free gear is dangerous like I said earlier, and you shouldn't save fuel by going into neutral unless your foot is on the throttle.

Adrian Wong · 14th May 2008, 06:20 PM

I just tried going downhill without coasting. The engine revs at about 1600 RPM (instead of 800-900 RPM at neutral) and I actually have to press the pedal to keep the speed up. In neutral, I actually pick up speed and the engine revs at a much lower speed.

Mac Daddy · 14th May 2008, 06:56 PM

You will save some petrol doing that Adrian but as mentioned your transmission and torque converter aren't designed for it. So over time you will shorten the life of your transmission. I coast in neutral quite a bit but I drive a 5 speed standard so its a bit different.

Same goes for people racing around using L1, L2 and Drive without a proper shift kit. Its not designed for it.

14th May 2008, 01:08 AM	#1 (permalink)
Adrian Wong Da Boss Join Date: 10 Oct 2002 Location: In front of my BenQ Joybook 7000 notebook! Posts: 29,655 Reputation: 2846 Rep Power: 63	[Auto Talk] Can regularly shifting to Neutral on an automatic gear damage it? Hi guys! I have an automotive-related question for the gearheads in this forum. My car has a 4-speed automatic transmission and I regularly shift to Neutral whenever I go downhill to let the car coast and save a little petrol. Of course, engaging the auto transmission after that can sometimes cause the engine to rev up suddenly. So I normally tap the pedal a little to rev the engine before engaging the auto gear. Someone recently told me that doing so will damage the automatic transmission. Is that true? Thanks! __________________ Dr. Adrian Wong Tech ARP \| Blog @ Tech ARP \| The Free Trade Zone DYKT : The only offshore account I have is at the sand bank? Keep Tech ARP free! Visit our sponsors! We need PROGRAMMERS and TECHNICAL WRITERS! Contact us if you are a hot shot programmer or technical writer! My items for sale : 50x SD Card \| Memory Stick PRO \| Cyclone Energy Saver \| Seiko SS watch \| Tiger/Carlsberg beer jugs \| Travel Speakers \| Motorola V600 \| Nokia N90 SOLD! \| New Lowepro Mini Trekker AW Other items for sale @ the FTZ : Zalman CNPS9500 LED @ $20 \| Zalman CNPS7700 Cu @ $20 \| Zalman CNPS7000 Cu @ $20 \| Swarovski bracelet watches \| Dell 17" LCD \| Hi-Fi speakers \| English DIVX movies \| HP LaserJet toners! \| Office chairs

14th May 2008, 04:00 AM	#2 (permalink)
wiiz Super Active Join Date: 28 Nov 2002 Location: KL Posts: 1,007 Reputation: 171 Rep Power: 8	the lesser you changing gear, the longer your gearbox last. ....and you dont have to put it in N, in D just lift off your pedal it still coasting. btw... Howstuffworks "How to Drive Economically: Tips and Guidelines" __________________ It's like finger pointing to the moon. Don't concentrate on the finger or you'll miss the heavenly glory - Bruce Lee

14th May 2008, 05:15 AM	#3 (permalink)
zy Dead Join Date: 16 Dec 2002 Location: Penang,Malaysia - Buffalo,New York Posts: 12,815 Reputation: 1998 Rep Power: 37	i think this doesnt really apply to modern cars. modern cars have advanced ECU, they should minimalize fuel compsumtion while you are coasting downhill. besides, while coasting downhill in neutral, your car engine still uses fuel to maintain the rpm even if you are in neutral. __________________ current: P4-3.2\|P4P800-Deluxe\|512x4-DDR\|NV6600 WD2500KS\|WD5000AAKS\|AD-7191A\|1860NX\|Z2300\|MP470 home (malaysia): P4C-2.6@3.1-StockHSF\|AI7\|256x2-BT-D43\|512x2-DT-D43\|A9600XT-VIVO WD1200JB\|2xWD2500KS\|DRU-800A\|DVD-E616P\|LTR-52327S\|152x\|V.S.4121\|iP1500 laptop: M1210\|T7200\|2GBDDR667\|160GB5K160\|GO7400

14th May 2008, 08:12 AM	#4 (permalink)
Chai Administrator Join Date: 6 Oct 2002 Location: Maranello Posts: 26,258 Reputation: 3845 Rep Power: 71	I think it's better to leave the gear in D while the car is moving, because you are not using more or less fuel as long as you are not on the pedal. Unlike manual cars, when your car is engaged to a gear, especially at high engine speed, your car will slow down even on a down hill slope. That's the reason why some like to shift to neutral, but it's dangerous. __________________ Chai (Contributor & Forum Admin) http://www.techarp.com/

14th May 2008, 08:56 AM	#5 (permalink)
PsYkHoTiK "Little" Devil Join Date: 8 Apr 2004 Location: On the "throne" Posts: 14,211 Reputation: 3938 Rep Power: 58	I wonder how much the torque convertor would like that. Coasting is bad practice IMO. Just how much can you save anyways? Plus coasting in gear may actually save you more gas (foot off throttle, the gas mixture usually cuts back as opposed to idling its still on). Plus engine braking wont wear out your brakes as much (aka coast in gear). Coasting in neutral is dangerous... __________________ Intel SLAPL 4.3GHz @ 1.35v : 2x2GB OCZ Platinum DDR2 1066 : Asus P5K Premium : WD Raptor X : G92 8800GTS 512mb 800MHz Core WIP : XFi Platinum : Silverstone OP650 : Silverstone TJ-07 : Vista Ultimate Edition : Dtek FuZion CPU : Swiftech MCW60 : MCP655 : Thermochill PA120.3 w Scythe Ultra Kaze : Tygon R3603 1/2" ID 3/4" OD CPU-Z: SLAPL : SLA9U : FX-55 : DDR 600 : VX www.techarp.com

14th May 2008, 10:28 AM	#6 (permalink)
Adrian Wong Da Boss Join Date: 10 Oct 2002 Location: In front of my BenQ Joybook 7000 notebook! Posts: 29,655 Reputation: 2846 Rep Power: 63	Actually, coasting in neutral can save a LOT. In city driving, I went from 8.5 km/l to about 10.5 km/l. On the highway, I went from 10 km/l to about 13 km/l. The thing is I have no idea if it's bad on the transmission. As for safety, I don't see how it can be a problem because I treat it like a manual shift. In the sense, I can shift out of neutral pretty quick (my hand is always on the shift stick). __________________ Dr. Adrian Wong Tech ARP \| Blog @ Tech ARP \| The Free Trade Zone DYKT : The only offshore account I have is at the sand bank? Keep Tech ARP free! Visit our sponsors! We need PROGRAMMERS and TECHNICAL WRITERS! Contact us if you are a hot shot programmer or technical writer! My items for sale : 50x SD Card \| Memory Stick PRO \| Cyclone Energy Saver \| Seiko SS watch \| Tiger/Carlsberg beer jugs \| Travel Speakers \| Motorola V600 \| Nokia N90 SOLD! \| New Lowepro Mini Trekker AW Other items for sale @ the FTZ : Zalman CNPS9500 LED @ $20 \| Zalman CNPS7700 Cu @ $20 \| Zalman CNPS7000 Cu @ $20 \| Swarovski bracelet watches \| Dell 17" LCD \| Hi-Fi speakers \| English DIVX movies \| HP LaserJet toners! \| Office chairs

14th May 2008, 12:49 PM	#7 (permalink)
PsYkHoTiK "Little" Devil Join Date: 8 Apr 2004 Location: On the "throne" Posts: 14,211 Reputation: 3938 Rep Power: 58	Coasting in gear with the throttle closed (aka foot off the pedal) closes your fuel injectors (aka not using fuel at all). Most of not all modern fuel injection systems cut off the fuel if not most of it while coasting in gear. However, it is not so when you are in neutral. Coasting is dangerous as the balance of your car is affected (try cornering with your car in neutral). It is a good reason why they made it illegal in some places. Not to mention in an emergency, you have much less reaction time (now that you have to get back in gear). As for your tranny, your torque converter will not like you. Plus with coasting you use up more of your brakes (tranny is a low wear component). I always engine brake when possible (and coast in gear). __________________ Intel SLAPL 4.3GHz @ 1.35v : 2x2GB OCZ Platinum DDR2 1066 : Asus P5K Premium : WD Raptor X : G92 8800GTS 512mb 800MHz Core WIP : XFi Platinum : Silverstone OP650 : Silverstone TJ-07 : Vista Ultimate Edition : Dtek FuZion CPU : Swiftech MCW60 : MCP655 : Thermochill PA120.3 w Scythe Ultra Kaze : Tygon R3603 1/2" ID 3/4" OD CPU-Z: SLAPL : SLA9U : FX-55 : DDR 600 : VX www.techarp.com

14th May 2008, 03:02 PM	#8 (permalink)
Chai Administrator Join Date: 6 Oct 2002 Location: Maranello Posts: 26,258 Reputation: 3845 Rep Power: 71	Very bad for torque converter. Coasting in free gear is dangerous like I said earlier, and you shouldn't save fuel by going into neutral unless your foot is on the throttle. __________________ Chai (Contributor & Forum Admin) http://www.techarp.com/

14th May 2008, 06:20 PM	#9 (permalink)
Adrian Wong Da Boss Join Date: 10 Oct 2002 Location: In front of my BenQ Joybook 7000 notebook! Posts: 29,655 Reputation: 2846 Rep Power: 63	I just tried going downhill without coasting. The engine revs at about 1600 RPM (instead of 800-900 RPM at neutral) and I actually have to press the pedal to keep the speed up. In neutral, I actually pick up speed and the engine revs at a much lower speed. __________________ Dr. Adrian Wong Tech ARP \| Blog @ Tech ARP \| The Free Trade Zone DYKT : The only offshore account I have is at the sand bank? Keep Tech ARP free! Visit our sponsors! We need PROGRAMMERS and TECHNICAL WRITERS! Contact us if you are a hot shot programmer or technical writer! My items for sale : 50x SD Card \| Memory Stick PRO \| Cyclone Energy Saver \| Seiko SS watch \| Tiger/Carlsberg beer jugs \| Travel Speakers \| Motorola V600 \| Nokia N90 SOLD! \| New Lowepro Mini Trekker AW Other items for sale @ the FTZ : Zalman CNPS9500 LED @ $20 \| Zalman CNPS7700 Cu @ $20 \| Zalman CNPS7000 Cu @ $20 \| Swarovski bracelet watches \| Dell 17" LCD \| Hi-Fi speakers \| English DIVX movies \| HP LaserJet toners! \| Office chairs

14th May 2008, 06:56 PM	#10 (permalink)
Mac Daddy Pickin' Da Gitfiddle Join Date: 19 Nov 2007 Location: Canada Posts: 2,048 Reputation: 802 Rep Power: 11	You will save some petrol doing that Adrian but as mentioned your transmission and torque converter aren't designed for it. So over time you will shorten the life of your transmission. I coast in neutral quite a bit but I drive a 5 speed standard so its a bit different. Same goes for people racing around using L1, L2 and Drive without a proper shift kit. Its not designed for it. __________________