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Unread 09-03-2009, 08:49 PM   #1
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Default does anyone have a strictly mechanical explanation as to why revving in an automatic

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

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Unread 09-03-2009, 08:52 PM   #2
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As long as you're in Manual when you rev in an automatic...I don't see how it makes a difference.

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Unread 09-03-2009, 09:53 PM   #3
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revving my old car didn't kill it (it was automatic, just over 4K RPM in park would kick in the rev limiter.
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Unread 09-03-2009, 10:32 PM   #4
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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.
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Unread 09-03-2009, 10:47 PM   #5
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Originally Posted by niightingale View Post
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
Do you mean putting the trans in neutral and revving it? Or revving it in park? Going from neutral to drive while revving it?
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Unread 09-03-2009, 11:09 PM   #6
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when people do it at stop lights =\

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Unread 09-03-2009, 11:16 PM   #7
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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.

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Unread 09-04-2009, 02:25 AM   #8
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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.
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Unread 09-04-2009, 10:54 AM   #9
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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.
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Unread 09-07-2009, 07:03 AM   #10
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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 [email protected] 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

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.

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