does anyone have a strictly mechanical explanation as to why revving in an automatic

[niightingale]

does anyone have a strictly mechanical explanation as to why revving in an automatic kills your car's engines? why is it that manuals are less affected by it? my friend briefly explained it and said something about manuals never being in gear but i don't exactly remember!

thanks thanks

[Retrospekt]

As long as you're in Manual when you rev in an automatic...I don't see how it makes a difference.

[cluffenstein]

revving my old car didn't kill it (it was automatic, just over 4K RPM in park would kick in the rev limiter.

[wierdo124]

I've never heard of such a thing.

I have, however, heard that shifting into neutral while going down a hill and letting the vehicle idle is hard on trannies

Personally transmissions are the area of cars i know least about.

[Speed_Demon]

does anyone have a strictly mechanical explanation as to why revving in an automatic kills your car's engines? why is it that manuals are less affected by it? my friend briefly explained it and said something about manuals never being in gear but i don't exactly remember!

thanks thanksDo you mean putting the trans in neutral and revving it? Or revving it in park? Going from neutral to drive while revving it?

[niightingale]

when people do it at stop lights =\

[Retrospekt]

when people do it at stop lights =\

Depends on if it's an idiot doing it or someone that knows anything. Someone smart will shift into neutral to do it. Someone who wants to wreck his tranny will put it in park or pull the e-brake and do it, which is stupid.

[KSIMP88]

Ummm, Only when you are in gear does it hurt an automatic, and only if you are fighting the car with the brakes. Both park AND neutral aren't in gear, so you are spinning nothing, just like revving with the clutch in while driving a Stick.

[Shrimpykins]

He said it will hurt it because automatics do not shift to neutral when at a stop unless manually shifted to neutral. A driver could keep his foot on the brake and give it gas at the same time, which can damage an engine and transmission. A manual on the other hand cannot do such a thing as it will kill the engine, unless the clutch is in, in which case you can rev the engine just like it is in neutral.

[evilgidget]

Revving an automatic car won't kill the engine. You can kill the transmission however.

In some vehicles, if the automatic transmission is in P or N, the high pressure fluid inside the transmission isn't being bled off through the various "workings" of the transmission. It then has to rely completely on a small bypass valve to control the pressure provided by the engine-driven pump inside the transmission.

What happens is the driver of the vehicle pulls up at the lights, sees a car full of pretty girls in the lane beside him so he sticks his car in neutral & revs the cr@p out of it to get their attention...
Meanwhile, inside the transmission... That poor little relief valve has to suddenly relieve a huge dose of fluid through it as the pressure pump maxes out. If it hasn't had a service in a while, the valve may not open fully. So the pump vanes bend & the pressure pump destroys itself. It's not a completely silent death, but it probably wasn't heard over the revved engine...
No pump means no fluid pressure. No fluid pressure means no drive. no drive means boy in car looks like a right Wally when the light goes green & gets smoked off the lights by the shopping-trolley hatchback full of girls :p

Revving it in drive with the brakes on is hard on a tranny because it's trying to move something that won't, so it cooks the fluid & wears the clutch packs. This won't destroy a tranny unless it was just about dead anyway, but that said burnt hydraulic fluid doesn't lube too well, so it does take it's toll eventually.

[Kenny McCormick]

Revving an engine too high, regardless of transmission, can damage it. With no load on it, the rods start to flop about a bit at high RPM, and they may start punching through the oil film that protects them. You get metal-to-metal, thusly, shortened bearing life. You may also throw a rod if the robot at the engine plant didn't torque the nuts enough on the rod caps, or if it torqued them too much and cracked them. You can also explode accessories, usually the alternator or power steering pump, that aren't designed to run that fast. It will also build heat, and since you aren't moving, the radiator may not be able to handle it. Some interference timing belt equipped engines that have been neglected might choose a no-load 8K stint to lose the timing belt.


The transmission is a different story....most have listed how it can damage an automatic, but that doesn't mean a manual is immune. In neutral, you can over-rev the gears and sling the fluid off(Remember, they're constantly meshing in there), you may prematurely wear out the input shaft bearings, and I'm sure the clutch won't appreciate. If you leave it in gear and hold the clutch down, you will very quickly heat up the throwout bearing and boil the grease out of it. They get noisy and gritty, and will fail quickly.

[KSIMP88]

Good thing this thread was answered before you two came. :p jk

[niightingale]

o__O


anyways, thanks for the explanations =]