10 replies to this topic

[SVX_commuter]

Has anybody with 4WD auto ever coasted in neutral with the engine running? What do you think of this? Will it damage the transmission?

Take care,
John

[zyewdall]

Well, I do in my manual tranny. I know they don't recommend it for manual or auto trannies, but obviously I don't listen...

[shaggywerewolf]

Well Subaru warns against towing the car in neutral (AT) with all 4 wheels on the ground. Isn't coasting in neutral basically the same thing? If it is, I suppose if you do this repeatedly, you could damage the transmission over time.....

[ferret]

Having had 5 speeds in all my Subaru's for 28 yrs, I have always taken the car out of gear and coasted up to Stop signs, red lights etc with no Ill effects.

As far as coasting in an Automatic, The only difference I see in the above statement between towing and coasting, is coasting with the engine running has the transmission front pump moving ATF thru the transmission thereby lubricating and cooling gears, clutches and assemblies. But I can't say if it will do any harm.

On the other hand, towing usually doesn't involve the motor running, hence miminal or no lubrication and no cooling.

[nipper]

Has anybody with 4WD auto ever coasted in neutral with the engine running? What do you think of this? Will it damage the transmission?

Take care,
John

There are several reasons for not doing this, and none of them have to do with tranmission damage. You wont hurt the auto tranny by doing this. On a manual there is a chance that you may not be able to get the car back in gear.
If you do do this, you loose the benefit of engine braking on steep hills, and can over work the brakes. Not only that, if the hill is steep enough, you would be amazed as to how quickly the car can pick up speed. Also there are two ways to avoid an accident, use the big pedla or use the little pedal. If you have to make an evasive manuver that envolves the little pedal, you may act by instinct and forget the car is in neutral, and precous time is lost.
Beleive it or not, in most states it is illegal to coast in neutral (impossible to enforce unless they scrape you out of the car and see it in neutral).

nipper

[hooziewhatsit]

I used to coast occasionally, until I found out that if you coast in gear, with your foot off the throttle (throttle plate closed) the ECU will actually stop or inject less gas than if you were idling in neutral.

[SVX_commuter]

I used to coast occasionally, until I found out that if you coast in gear, with your foot off the throttle (throttle plate closed) the ECU will actually stop or inject less gas than if you were idling in neutral.

Yes I have heard that also, less gas with the throttle plates closed. What do you think about the engine braking effect? If this is true then the ECU must somehow figure out the engine is used being used for braking and tries to cut the gas to help it slow down. I wish I had a scan-gauge that measured mpg for car but it won't work on a 92. It would be an easy way to check on this.

[SVX_commuter]

Beleive it or not, in most states it is illegal to coast in neutral (impossible to enforce unless they scrape you out of the car and see it in neutral).

nipper

Yes it is illegal in my state too. I have noticed an effect on coasting when a relatively simple mod is done. This is done by disconnecting the dropping resistor for the transmission line pressure. The tranmission does not allow engine braking to occur when this resistor is disconnected. This will allow the car to "free wheel" down the hills. So the car would not be coasting in nuetral for this "modification". Is there any other problems besides the power light (TCU) blinking all the time at start-up and the line pressure from the ATF pump at maximum all the time?

[2X2KOB]

Why is it that you want to do this?

[zyewdall]

There are several reasons for not doing this, and none of them have to do with tranmission damage. You wont hurt the auto tranny by doing this. On a manual there is a chance that you may not be able to get the car back in gear.
If you do do this, you loose the benefit of engine braking on steep hills, and can over work the brakes. Not only that, if the hill is steep enough, you would be amazed as to how quickly the car can pick up speed. Also there are two ways to avoid an accident, use the big pedla or use the little pedal. If you have to make an evasive manuver that envolves the little pedal, you may act by instinct and forget the car is in neutral, and precous time is lost.
Beleive it or not, in most states it is illegal to coast in neutral (impossible to enforce unless they scrape you out of the car and see it in neutral).

nipper

There are some long even hills on the freeway here that are the perfect slope to go down at 75 in nuetral. If I have it in gear, I have to keep my foot on the gas to keep the rpm's up at 3500 to keep it from slowing down. But that's a very special case. In general I agree, keep it in gear to use engine braking. As far as using the gas to avoid an accident, if there are other cars closeby, I usually don't do the coasting thing for that reason, though at that speed, an EA82 can't really accellerate anyway...

[Legacy777]

Just a note, don't ever cost with an automatic and the engine not running. The automatic trans get's its lubrication from the pump in the transmission. When the engine isn't running, it doesn't get lubricated.

As for your circumstance....personally, I wouldn't bother with putting the car in neutral.