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Putting an A/T in neutral while stopped?


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8 replies to this topic

#1 TROGDOR!

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Posted 13 October 2003 - 09:58 PM

A while back my dad told me that it's gentler on an automatic trans to put it in neutral while at a stoplight. I have noticed that when I do this I don't have to hold the brake pedal as hard, and that the car idles smoother.

So here's what I've been debating...

Putting the trans in neutral saves wear by not forcing the transmission to run while the car is stopped.

However, having to put the car back in gear whenever you want to get going again adds a lot of unneccessary shifting in and out of gear, which could cause extra wear.

So which is better?

#2 JWX

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Posted 13 October 2003 - 11:27 PM

I do this with my Rolla and I don't see anything wrong with it, yet wouls like to get the word from somebody who knows though

#3 calebz

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Posted 13 October 2003 - 11:34 PM

I would tend to think the advantages would be minimal unless stopped for a really long time.. Remember the auto tranny is designed to sit at a stoplight while still in gear

#4 Ratty2Austin

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Posted 14 October 2003 - 12:37 AM

Dude! thats totally how I drive autos! I drive the delivery subaru at work like that, and my impreza, and everythign auto! (I hate that annoying feeling that if i lift my foot up the car starts going forward)
and i think it is easier on the car, in fact it is easier on the brakes as well! (needs less force to slow to a stop cause the car is no longer pushing forward)

i suggest using neutral often!

#5 electryc_monk

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Posted 14 October 2003 - 12:45 AM

auto tranny trivia just got more intense.

i read somewhere over the summer that there is a "Standard" for push starting even an automatic tranny as well as a worning for limited towing distances if having to tow on all fours.

funnny thing is the ability to use the auto tranny for push starting is 25-35 mph MAX in "D" and the towing in neutral is not allowed over 25 MPH for more then 8 or 10 miles. otherwise dameage is certain in said design of trannies.

now about the "neutral stopping..."
I'd personally liken it to neutral stopping in a stick.....
I have done it many times with many different cars... most notibly the Caddies in the family.
no adverse or even negligable problems came of it...and I even talked with different "mechanicas" even asked it in the auto tranny rebuild class at the JC i was in... the teachers reaction. "It won't hurt it, unless your trying to do a neutral drop at a stoplight and THAT will damage it in short order.

#6 Setright

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Posted 14 October 2003 - 01:11 AM

Trogdor!

The out going transmission axles are NOT moving when the car is standing still, so there is no mechanical wear on bearings or cogs. The "torque converter" or "fluid coupling" between the engine and trans is where the action goes down while stopped in "D".

Bascially, but not accurate in detail, since it would take to long to explain:

The converter consists of three turbines sat in the same oil filled housing. One is spun by the engine, one is attached to the trans oil pump, and the last drives the trans input axle. The second two tend to follow the first, with roughly 3% loss in the oil.

Stopped in D, the trans input axle turbine is not allowed to move and provides resistance to the oil flow in the converter housing. Slipping into N allows the turbine to spin along with the oil. The pump turbine will be spinning in either case, driving the trans oil pump.

The N at lights is therefore less stressful for the ENGINE, and keeps the torque converter oil temperature down and will lessen the amount of foaming of the trans oil.

The added shifting causes minimal wear, so long as you do it at idle speed!

#7 MilesFox

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Posted 14 October 2003 - 01:41 PM

josh has an 03 legacy, and if he gets out of the car while its running, its in neutral with the parking brake.

when i drive an uato i will leave it in neutral at a long red light or the drive thru

its less shifting to gto from d to n than it id to go from d to n to r to p!

#8 Hondasucks

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Posted 14 October 2003 - 02:13 PM

First off, when you "stall" the torque convertor, such as at a red light, it generates heat. Putting it in neutral causes it to not stall the converter, so it won't build up heat. (In fact, if you take an auto tranny, put it in Drive, hold the brakes and mash the trottle, (called a Stall test, if the engine RPM doesn't go above about 1500 RPM you are OK, but if it jumps up to 3-4000 RPM, you know your tranny is slipping) for about 30 seconds, the fluid will get so hot it will boil, and shoot the dipstick out :-) Dont' do it, it will cook the tranny.

Also:

"The converter consists of three turbines sat in the same oil filled housing. One is spun by the engine, one is attached to the trans oil pump, and the last drives the trans input axle. The second two tend to follow the first, with roughly 3% loss in the oil"

Not entirely true. A T/C does consist of three turbines, the impeller, which is attached to the crankshaft, the turbine, which is attached to the input shaft of the transmission, and the stator, which is what does the torque multiplication. The hydraulic pump is driven off of the torque converter housing itself. Where the housing goes into the transmission case, there is a lug that drives the oil pump. Since the oil pump is driven OFF THE ENGINE, is why you can't push-start an automatic, since it requires hydraulic pressure, generated by the pump, to engage the gears.

#9 Nug

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Posted 14 October 2003 - 03:02 PM

There were some OLD old fashion automatics (Buick?) that had an ancillary pump that was driven off of the tailshaft, which would engage a clutch when the car was pushed, allowing the car to be push-started. 50-60 years ago, I guess.




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