Automatic Transmissions in General

This is a noob question I have asked people what would happened if I put a automatic transmission in neutral down a hill lets say in traffic .I got different responses some say it hurts the transmission some say it doesnt do anything does anybody know if it hurts the transmission or not if I coast in neutral down a hill.
 
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This is a noob question I have asked people what would happened if I put a automatic transmission in neutral down a hill lets say in traffic .I got different responses some say it hurts the transmission some say it doesnt do anything does anybody know if it hurts the transmission or not if I coast in neutral down a hill.

Besides being unlawful and perhaps dangerous why would you want to do that. If there is no need for fuel the PCM will stop the fuel flow through the injectors so you are not saving gas.
 
Besides being unlawful and perhaps dangerous why would you want to do that. If there is no need for fuel the PCM will stop the fuel flow through the injectors so you are not saving gas.

While I can't say for sure on a gas vehicle, my Superduty always gained MPG when I would free wheel up to a redlight or stop sign, I know that for a fact. The converter stayed locked and kept the engine spinning at a higher RPM than necessary. If the engine is running, there is fuel being used, so you may not gain much on a gasser in the long run.

My question is why do you say it's unlawful?? If it were unlawful to put the tranny in neutral, how could any of us drive a stick? Not being a jack, just curious what laws could come into play with this situation.
 
i used to do that when i drove a stick

now, my aod behaves like you are describing (converter locked in 3rd causing engine braking and bringing up the rpms) and i sometimes am tempted to put it in neutral, but one time i tried to do it and i mistakenly moved it too far and put it into reverse intead. i immediately got it into neutral, but that reverse clunk didn't sound good, and i haven't tried it since. lucky for me i wasn't going very fast.
 
Besides being unlawful and perhaps dangerous why would you want to do that. If there is no need for fuel the PCM will stop the fuel flow through the injectors so you are not saving gas.

Unlawful:shrug: I just was curious I sometimes do it when Im in traffic going down a two mile hill going maybe 10 -20 miles an hour and it has saved me gas by doing this method but I was worried about the transmission thats all
 
1. you are not saving but a couple drops of gas.
2. its not going to hurt the tranny, the converter spins all the time, its attacked to the flywheel, the impellers inside it will change speed.
3. keep it in drive...its just smarter.
4. diesels do not have engine breaking, they are not like gas engines.
 
when i still had the aode going down a large hill i would turn off the overdrive to slow me down so i would'nt have to ride the brake's,thats what your supposed to do.i dont see how putting the car i neutral would hurt the tranny.
 
Unlawful:shrug: I just was curious I sometimes do it when Im in traffic going down a two mile hill going maybe 10 -20 miles an hour and it has saved me gas by doing this method but I was worried about the transmission thats all

My reference to coasting being unlawful was specifically related to the British Columbia Motor Vehicle Act. The prohibition is as described in section 197:

Coasting down grade
197 When travelling down grade a driver must not coast with the gears of the vehicle in neutral or the clutch disengaged."

It is my understanding that most state MVA's also contain a similarly worded clause.
 
The torque comvertor locks the third and overdrive clutches at cruising speeds(highway speeds).

I don't see how putting the tranny in nuetral will aid in fuel economy, so I would just leave it in drive.

I think what toyman is getting at is the 'friction' caused when the car is in gear will aid in slowing the car down, especially on a down grade. Otherwise, you need to use your brakes more; and you could end up with a 'runaway semi' senerio.