AT netural downhill

Island_370 · 03-19-2012, 07:50 PM

Quote:

Originally Posted by wilsonp

As Click and Clack point out, new brake pads are cheaper than a new transmission, so don't put extra wear and tear on the drivetrain for slowing down on hills. Use the parts as they are intended.

I believe they are talking about downshifting to slow the car in place of using the brakes. Not leaving the car in gear when going down hill.

JohnTrang · 07-11-2015, 12:33 AM

New Z owner and had the same question. I always coasted downhill with my automatic Civic and after 16 years no transmission problems (that I know of).

But my Z really slows down when off the gas, even downhill. The Z also has stickier tires. I'll try paddle shifting to a different (higher?) gear.

The 2015 owners manual P 5-13 says "Caution: Coasting with the transmission in the neutral position may cause serious damage to the transmission".

Zipper 104 · 07-11-2015, 02:44 AM

Quote:

Originally Posted by Felix 808

Actually I am going to say it is a bad practice on a few reasons.

1. You never tow an automatic with wheels on the ground in neutral- The trans pump is not pumping vital fluid for cooling. Coasting in neutral would simulate the same conditions, causing excess heat (#1 AT destroyer).

2. Delay in power if you need to gain speed for any reason

$.02 YMMV

Number 1 absolutely. The car must be left running if you're going to coast in neutral in an automatic.

104

Zipper 104 · 07-11-2015, 02:46 AM

Quote:

Originally Posted by harman.khinda

hypothetically - turning off your car as you cost downhill and then turning it back on at the bottom would save the most gas.

Yup....it'll save more gas but not money. You'll be replacing the tranny.

104

Megan370z · 07-11-2015, 03:25 PM

quite a bit of miss-information in here.....

coasting down a hill with the 7AT in neural will not save you any money as the engine will be idling and using gas. When coasting in gear, the rpms will be held by the transmission and the injector will not inject fuel.

best way to see this is with an wideband gauge or dataloging your O2 sensor when driving.

Catallaxy · 07-14-2015, 05:14 PM

Well, just to clarify, if your engine is idling, the injectors are opening. They're just running a vastly smaller duty per cycle. So they're open for a shorter period of time. If the injectors remain closed, your motor isn't running.

As for the mission; there's still fluid flow. The pressure is mostly maintained by the ECU. The issue is the sudden gear engagement when you need to accelerate again.

It's like trying to clutch start a manual: dumping the clutch in gear while rolling is bad news. Same issue with an automatic. Engaging those "gears" (they're clutch packs, really) while moving is sudden force on those parts.

I advocate leaving the car in gear, using a combination of engine braking and the cars actual brakes. That should help minimize wear on either part.

JC-Nismo · 07-14-2015, 05:25 PM

I've coasted downhill in neutral in MT cars for over 20 years and never had any issues. I don't know where you guys get this theory from, but to each his own.

Megan370z · 07-14-2015, 06:52 PM

Quote:

Originally Posted by JC-Nismo

I've coasted downhill in neutral in MT cars for over 20 years and never had any issues. I don't know where you guys get this theory from, but to each his own.

really ?

not sure if serious....

let me subscribe off this thread, I thought it was about the 7AT...

07-11-2015, 03:25 PM	#20 (permalink)
Megan370z A True Z Fanatic Join Date: Oct 2009 Location: Canada Posts: 1,156 Drives: 370z Rep Power: 24	quite a bit of miss-information in here..... coasting down a hill with the 7AT in neural will not save you any money as the engine will be idling and using gas. When coasting in gear, the rpms will be held by the transmission and the injector will not inject fuel. best way to see this is with an wideband gauge or dataloging your O2 sensor when driving. __________________ Megan Journal Click Me ....................One Man Team Motorsport Click Me

07-11-2015, 12:33 AM	#17 (permalink)
JohnTrang Base Member Join Date: Sep 2014 Location: North Alabama Age: 52 Posts: 47 Drives: 2015 370Z Sport Tech Rep Power: 11	New Z owner and had the same question. I always coasted downhill with my automatic Civic and after 16 years no transmission problems (that I know of). But my Z really slows down when off the gas, even downhill. The Z also has stickier tires. I'll try paddle shifting to a different (higher?) gear. The 2015 owners manual P 5-13 says "Caution: Coasting with the transmission in the neutral position may cause serious damage to the transmission".

07-14-2015, 05:14 PM	#21 (permalink)
Catallaxy Base Member Join Date: Jun 2015 Location: Texas Posts: 3 Drives: 2013 370Z Rep Power: 10	Well, just to clarify, if your engine is idling, the injectors are opening. They're just running a vastly smaller duty per cycle. So they're open for a shorter period of time. If the injectors remain closed, your motor isn't running. As for the mission; there's still fluid flow. The pressure is mostly maintained by the ECU. The issue is the sudden gear engagement when you need to accelerate again. It's like trying to clutch start a manual: dumping the clutch in gear while rolling is bad news. Same issue with an automatic. Engaging those "gears" (they're clutch packs, really) while moving is sudden force on those parts. I advocate leaving the car in gear, using a combination of engine braking and the cars actual brakes. That should help minimize wear on either part.

07-14-2015, 05:25 PM	#22 (permalink)
JC-Nismo A True Z Fanatic Join Date: Sep 2014 Location: Atlanta Posts: 1,244 Drives: 2011 Nismo 370z Rep Power: 13	I've coasted downhill in neutral in MT cars for over 20 years and never had any issues. I don't know where you guys get this theory from, but to each his own.