Shifting from Neutral to Drive

[Clemsonfan15]

One of my friends suggested shifting from drive to neutral during long downhill sections of road in order to save gas. So my question to you is is it harmful to my transmission? I have an automatic if that makes a difference.

 

[CJ3Flyr]

If you leave the engine running then you're fine. A/T's can be damaged by coasting or towing with the engine off as the internals don't get lubed properly. Happy coasting

:cheers:

 

[Clemsonfan15]

Alright, thanks. The car does shake (shake maybe the wrong word) a little when I shift it back into drive, but I guess that's just the gears reengaging.

 

[Justinlhc]

In the owners manual of my Chrysler it says that damage will occur if the vehicle coasts in neutral. They don't say if it matters if the engine is running or not. I do it with manual trannys as much as I can, but obviously that's different.

 

[Climb14er]

Alright, thanks. The car does shake (shake maybe the wrong word) a little when I shift it back into drive, but I guess that's just the gears reengaging.

It's one of the worst things you could do to an auto tranny!

First of all, you disconnect the driveline's/engine's ability to slow and control your vehicle. Second, the releasing and engaging of the tranny places stress on the tranny and driveline itself. You might not think so, but continued use is ill advised.

Manual trannys don't have the same problems in doing so as with autos. I still recommend not going in neutral down long hills and passes... you'll pick up too much spped that when you need to re-engage the tranny, you'll load up the driveline and tranny itself.

Go ahead... it's your vehicle... personally, I see absolutely zero savings from this for what you 'might' save with fuel, you'll lose with stress and wear to the components.

 

[Clemsonfan15]

It's one of the worst things you could do to an auto tranny!

First of all, you disconnect the driveline's/engine's ability to slow and control your vehicle. Second, the releasing and engaging of the tranny places stress on the tranny and driveline itself. You might not think so, but continued use is ill advised.

Manual trannys don't have the same problems in doing so as with autos. I still recommend not going in neutral down long hills and passes... you'll pick up too much spped that when you need to re-engage the tranny, you'll load up the driveline and tranny itself.

Go ahead... it's your vehicle... personally, I see absolutely zero savings from this for what you 'might' save with fuel, you'll lose with stress and wear to the components.

Ok. That's what I expected. I have gotten a little better gas milage, but I don't want to harm the tranny at all. I'm going to stop using this method.

Thanks for the input everyone.

 

[rook]

most modern toyota efi systems are programmed to turn injectors off when coasting in gear. (closed throttle)

coasting in neutral will keep the injectors firing, but remove pumping losses so you will coast faster but burn fuel in doing so

 

[Clemsonfan15]

I have a '98. I'm not sure if the "modern" Toyotas your talking about cover my 4runner.

Are you saying it is ok or not ok to shift from neutral to drive, at say 60 MPH(I'm not sure if speed makes a difference).

 

[peter78]

About a month I remember reading the car guys, or whatever they are called, in the local paper. Some guy wrote in and he put the car in neutral and when he put it back in drive, the transmission made a terrible sound and blew apart. The car guys said he accidentally put it in reverse. Ouch, that hurts. :awais:

 

[Clemsonfan15]

I always wondered what would happen if I did that. I guess I dodged a bullet so to speak. When I was really trying to save gas I would probably shift back and forth 15+ times a day.

 

[Uneek]

Personally, I think the danger without engine braking negates any gas savings.

I'm not a mechanic, but I think with the driveshaft spinning a high rate of speed and the engine at a lower speed when it's back into gear can't be good for the transmission. Whereas on a manual, you can probably match the speed and get it in the correct gear would match RPMs to speed.

 

[MikesToy]

It is NOT ok to shift from drive to neutral while going downhill. It will mess up your transmission. You probably save .50 cents worth of gas everytime you do it. But it doesn't add up for a new transmission.

 

[ALt4r]

Don't shift in between neutral and drive at high speeds, its just dangerous and not worth the amount of gas you would save.

 

[rook]

many here are missing the point.. you are NOT saving gas by shifting into neutral... all modern toyota efi systems.. (since the early '90's) detect that non-neutral closed throttle conditiion, and turn off the pulse to the injector.. so, you can coast in neutral and burn fuel, or coast in gear and not burn fuel...

Has anyone consulted the owners manual to see if it will cause damage?

 

[FT5117]

I have an automatic if that makes a difference.

I wouldn't recommend, especially if you have an A/T. Here's a general rule of thumb: try to shift as little as possible... For example, when you find a parking space, try to find one where you can park in the next slot in front of you, this way when you leave, you can just drive off, and not have to go from Park to Reverse, stop, then shift to Drive. One of the old school ways to test if a transmission is worn, is shifting (while stopped) from P to D, wait a moment, then shift to R, wait, shift back to D, repeat as needed. If there's no loud clanking then the A/T is likely in good condition.

If you really want to save gas, then check out this segment from Mythbusters. It's about drafting behind a semi-truck. Here in Los Angeles, tailgating is normal due to constant heavy traffic, etc. But do so at your own risk. Semi drafting really works, helped improve my V8 2wd from 22mpg to a whopping 24.5mpg, based on mostly highway driving. If you do try it, make sure you pick a semi that has decent mud guards on the rear tires. I try to keep at least 3-4 car lengths between me and the truck, seems a lot safer than driving behind other cars / suvs that tend to brake more suddenly and more frequently.

DRAFTING SEMI
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[Clemsonfan15]

Re: Re: Shifting from Neutral to Drive

I wouldn't recommend, especially if you have an A/T. Here's a general rule of thumb: try to shift as little as possible... For example, when you find a parking space, try to find one where you can park in the next slot in front of you, this way when you leave, you can just drive off, and not have to go from Park to Reverse, stop, then shift to Drive. One of the old school ways to test if a transmission is worn, is shifting (while stopped) from P to D, wait a moment, then shift to R, wait, shift back to D, repeat as needed. If there's no loud clanking then the A/T is likely in good condition.

If you really want to save gas, then check out this segment from Mythbusters. It's about drafting behind a semi-truck. Here in Los Angeles, tailgating is normal due to constant heavy traffic, etc. But do so at your own risk. Semi drafting really works, helped improve my V8 2wd from 22mpg to a whopping 24.5mpg, based on mostly highway driving. If you do try it, make sure you pick a semi that has decent mud guards on the rear tires. I try to keep at least 3-4 car lengths between me and the truck, seems a lot safer than driving behind other cars / suvs that tend to brake more suddenly and more frequently.

DRAFTING SEMI
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Interesting idea. I have watched that episode before. I don't do much highway drive though. Maybe an average of 10 miles a week if that.

 

[Climb14er]

Re: Re: Re: Shifting from Neutral to Drive

Interesting idea. I have watched that episode before. I don't do much highway drive though. Maybe an average of 10 miles a week if that.

Just like you were told by your friend that it's ok to shift from D-N-D to save gas... which is a ridiculous idea, drafting a semi is one of the most dangerous things a driver could do.

If the semi blows a capped tire, you'll be smeared by rubber head on into your vehicle or windshield at high speed. Guess who wins when this even occurs?

If the semi has to stop quickly, where do you think your vehicle is going to go?

 

[Clemsonfan15]

Re: Re: Re: Re: Shifting from Neutral to Drive

Just like you were told by your friend that it's ok to shift from D-N-D to save gas... which is a ridiculous idea, drafting a semi is one of the most dangerous things a driver could do.

If the semi blows a capped tire, you'll be smeared by rubber head on into your vehicle or windshield at high speed. Guess who wins when this even occurs?

If the semi has to stop quickly, where do you think your vehicle is going to go?

Shifting to N auctually did save gas.

I wouldn't draft a semi though. I think in that test on Mythbusters they were like a foot away or something? Bad idea.

 

[Hayn4R]

I actually shift to N all the time coming downhill on the freeway.

I dont hear or feel anything. When I need to slow down, I just put it back into D.

I think Toyota made a tough enough tranny to accomodate this habit.

 

[sn0wrunner]

The car guys said he accidentally put it in reverse. Ouch, that hurts. :awais:

This happened to me about two years ago. I was going 15 or 20 mph and my brother's foot accidently hit the the shifter and knocked it into reverse. (I'm not sure what he was doing with his feet, lol, he was 10 or 11) The engine just shut down. I coasted to a stop and it turned right back on thankfully.

I think I got a little lucky. I shit my pants when it happened though.