Driving & waiting in neutral

[scottydl]

These two questions really apply to any car, not just Auroras... but I'm hoping someone who knows about the mechanics of transmissions can chime in:

(1) I've heard it's bad to put the tranny in Neutral while the car is moving, especially at a high rate of speed... why is that? Is the actual "free roll" that is not recommend, or the strain from changing the gears back and forth while they're spinning?

(2) A few years ago I bought a '92 Caprice 9C1 (police package) with 150k miles. It had a rebuilt LS1 engine, but the original tranny which performed flawlessly. The previous owner said I could prolong the life of the tranny by shifting into Neutral whenever I was waiting in traffic or at a stop light. Is that true, and should all cars be treated that way for maximum tranny life?

[Custom88]

1. I"m not positive as to why it's bad but I do know that you cannot tow a front wheel drive car with the drive wheels on the ground in neutral. It will destroy the transmission. I have also noticed that if you have both front wheels jacked off the ground with the car in neutral and spin one wheel, the wheel on the opposite side of the car spins in the opposite direction. When forcing both to go forward against how it would naturally turn might have something to do with it maybe?

2. I'd think shifting into neutral at every light would cause more wear and tear because of the constant engaging/disengaging of the drive gears. I do think if you're going to be idling for a long time it might be a good idea but just for stop lights, no.

[Aurora40]

At idle, I wonder too which is better for the tranny and the engine. Not sure if it would really make a big diff either way. When stopped, the torque convertor is just sloshing fluid around to dissipate that idle power. It might make a bit more heat, but I'm not sure.

At speed, if you put it in neutral, your engine will presumably go to idle. This means the input to the tranny is turning very slow and the tranny pump would not be able to pump much fluid. This could possibly cause starvation or overheating of parts, but I think you'd have to sustain that for a bit for damage to happen. I don't think it's a good idea, though.

What I do know is the tranny was designed to perform when used normally/properly (in D all the time). So this would be the safe bet in light of uncertainty about the other alternatives. You could also ask it on the caddy board in the Northstart section. I bet there are some folks intimately familiar with the 4T80-E who could shed some light.

[SupaStealth]

when i got my first car i put the car in neutral down hills. as well as my second car, i burnt up both of them, although the first one, my dad decided that it was ok for a 86 buick lesabre with the 3800 motor to pull a 1970's Ford Diesel Tractor because my car had a tow hitch. i figured what the hell, he bought the car, it was his choice, heh. when we were goin' up a hill the tranny was burnin up. 3 months later it started slipping. so i'm assuming that was the problem. with my second car, 1989 Olds 98 also with the 3800 motor. i also put the car in neutral down hills to get better gas mileage, and after driving for 8 months it started not shifting into overdrive, then drive, then 2nd. So yeah, i try not to go into neutral while i'm moving.

i definitley know that it's bad to have the car shut off and coast, i believe that it doesn't get lubricated if the car isn't running. one time we(my parents and i) happened to run out of gas on the freeway and coasted for two miles somehow, up an onramp and just barely got to the driveway of a gas station. since then the car has a hard time shifting from 1st to 2nd gear. but it hasn't gotten any worse surprisingly

[stevensolds]

i leave it in drive; except when i wanna shift it from 1st -> 2nd -> 3rd etc what the hell would you rather replace an expensive tranny or use a tiny bit more gas?

[Marc]

The only times I ever had to put the trans in neutral was
with my prior car, a 1972 455 442 W-25. This car was
not good in stop & go traffic....vapor lock, carburetor
icing and eventual plug fouling would occur if the RPMs
were not kept up at low speeds.


_________________

GM!!! BRING BACK OLDS!!!

[Letitroll98]

And with DIC in fuel economy mode, you can see that your instantaneous mileage goes up to 68 mpg or something when coasting in drive anyway. So there really is no need to shift into neutral for gas mileage.

The best way to improve fuel economy is to not apply the brakes. Internal combustion engines are very efficient at converting gasoline to speed vs. distance at around two thirds throttle. Note that this is not related to your DIC reading, but is a function of the tradeoff of speed and distance. However gains made in this formula are lost the minute you apply the brakes and transfer all that kinetic energy gain into heat dissipated from the brakes. This is why you get so much better mileage on the highway vs. city stop and go.

You can however still modify many aspects of you city driving to improve fuel economy, without having to drive like a granny from the stoplight. Remember that braking is the enemy, not accelerating. Coasting up to stops, lightly applying brakes, leaving longer following distances to facilitate this, etc. will all get you better mileage.

I myself don't follow any of these procedures to save the planet's resources. The heck with the grandkids, I gotta get somewhere now! I'm headed out presently to burn as many dead dinosaurs as I can in my big V8 4,000lb sedan, banking on being dead before our fossil fuel reserves are used up.

[Aurora40]

Letitroll98 said:

I'm headed out presently to burn as many dead dinosaurs as I can in my big V8 4,000lb sedan, banking on being dead before our fossil fuel reserves are used up.

Try to apply at least a little foresight, though. You don't want to become dead before the fossil fuel reserves under your trunk are used up...