Transmission question

[sebaz]

My boss and I have an ongoing discussion about this: I always thought that when you're stopped at a red light for a long time, let's say over 20 seconds, you should set the gear to neutral on automatic transmissions. To me if you're pressing the brake constantly for several seconds it hurts the transmission and/or the engine, because the car is being forced to be still but the engine is still trying to traction. And recently I asked this to my mechanic, a guy that has over 20 years of experience, and he told me it's true, that my reasoning was correct. However, my boss says that shifting to neutral on almost every red light puts a lot of unnecessary wear on the transmission. She has a point there, so I thought I would post a message here about it, and maybe some knowledgeable folks could give me some light on this. And if my reasoning is correct, is this the same for every car, and for different typees of vehicles, such as a van as opposed to a regular sedan such as a LeSabre or a Camry?

Thanks,

Sebastian

[beef_bourito]

the transmissions are designed to be able to stay in gear while the engine is stoped. this is done through the tourque converter, it's basically a fan in a think liquid that turns another fan, the engine turns one fan and if the braks are on the other one wont turn. the only thing i can see is that the liquid in the tc (tourque converter) heats up a bit and there is a bit of extra strain on the tranny because of the constant force on it. i think that shifting into and out of neutral however might add more strain than it relieves because when you shift into gear there will be a sudden aplication of tourque although small that will cause strain. the cars are designes so that people drive them in gear all the time, mostly because thats how people drive them anyways.

[sebaz]

Originally Posted by beef_bourito

i think that shifting into and out of neutral however might add more strain than it relieves because when you shift into gear there will be a sudden aplication of tourque although small that will cause strain. the cars are designes so that people drive them in gear all the time, mostly because thats how people drive them anyways.

Thanks for your reply. Now, let me ask you, when I have the green light and I shift into gear I do it without pressing the brake pedal, do you think that in that case there is still strain?

Thanks,

Sebastian

[beef_bourito]

i don't think there is as much strain being put onthe engine. think of it this way what hurts your hand more, hitting a nail with a hammer and driving it in or hitting a wall that doesn't move. it's not this drastic, i mean there shouldn't be that much strain, but it's similar. besides, you'll probably sell your car before the tranny dies from any added strain from shifting in and out of neutral. when you're moving however, if you shift into neutral and then want to shift into gear, it helps to give a bit of gas to match the revs to what they should be at that speed before shifting back into gear.