Why do they make auto transmissions do this?
03-03-2005, 08:27 PM
#1
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Location: South Jersey
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Why do they make auto transmissions do this?
Why do they build in "creep" into automatic transmission cars? It drives me crazy whenever I drive one. I take my feet OFF the pedals and the car tries to drive away. Who wants that? 
It makes even less sense considering all the safety crap that is mandated (can't put it in D w/o a shift interlock but if I do the car will drive away by itself ).
Is there some technical reason?
(I know this is more of a lounge question, but I figure someone here actually knows the answer!)
It makes even less sense considering all the safety crap that is mandated (can't put it in D w/o a shift interlock but if I do the car will drive away by itself ).Is there some technical reason?
(I know this is more of a lounge question, but I figure someone here actually knows the answer!)
03-03-2005, 08:47 PM
#3
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Re: Why do they make auto transmissions do this?
Even at idle, one half of the torque converter is still turning 600 rpm, throwing oil at the other half which is less than an inch away. Some power is bound to be transmitted. Also, by having the torque converter slightly engaged at idle, it makes the step-off more immediate without having to wait for the TC to 'spool up'.
03-03-2005, 10:09 PM
#4
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Re: Why do they make auto transmissions do this?
The three cars I've owned both did this bad(91 Regal, 90 Caddy STS, and the Z). Whenever I drive an auto car that doesn't do this, it drives me nuts.
03-04-2005, 03:01 AM
#10
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Re: Why do they make auto transmissions do this?
Thats when you turn it into a manual and throw it in nuetral. I do it all the time when I have an automatic.
In Visalia, Ca they have bomb (lowrider) races, where they put it in drive and the last to cross a line is the winner. I think they do it every week in the summer.
In Visalia, Ca they have bomb (lowrider) races, where they put it in drive and the last to cross a line is the winner. I think they do it every week in the summer.
03-04-2005, 07:13 AM
#11
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Re: Why do they make auto transmissions do this?
Autos are suppose to do this. I dont see what the problem is. If you want to sit there with it running and not touch a pedal, put it in park. When you say "who wants them to do this?", I can answer that I freaking do. Sit in trafic going 3 mph for an hour and tell me the way this works is not the best possible way.
03-04-2005, 08:00 AM
#13
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Re: Why do they make auto transmissions do this?
When the shifter is in "D", the car is in gear. Try putting a manual transmission in gear with the engine at idle. It will move (unless it stalls, of course).
As was said, you can take the car out of gear, just like one does with a manual (except with an auto, you get two choice - park and neutral).
03-04-2005, 08:24 AM
#14
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Re: Why do they make auto transmissions do this?
A torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. If the engine is turning slowly, such as when the car is idling at a stoplight, the amount of torque passed through the torque converter is very small, so keeping the car still requires only a light pressure on the brake pedal.
The creep is just a function of the torque converter. Unless you put it neutral or park nothing you can do about it.
The creep is just a function of the torque converter. Unless you put it neutral or park nothing you can do about it.
03-04-2005, 08:28 AM
#15
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Re: Why do they make auto transmissions do this?
Okay, so it is normal to have to apply light brake pressure...
Except my Z28 will roll at 25 or 30, once I get it there, without having to touch the brakes... And I have to virtually stand on the brake to keep it from moving at a light...
I bought the car with a bunch of mods done, is it possible that an aftermarket torque converter is causing this? I know my previous car, a 96 RS, didn't do that.
All I know for sure that's been done to the car is the supercharger, headers, exhaust, and the rear end has been built...
Except my Z28 will roll at 25 or 30, once I get it there, without having to touch the brakes... And I have to virtually stand on the brake to keep it from moving at a light...
I bought the car with a bunch of mods done, is it possible that an aftermarket torque converter is causing this?
I know my previous car, a 96 RS, didn't do that.All I know for sure that's been done to the car is the supercharger, headers, exhaust, and the rear end has been built...