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transmission when in drive with no gas wants to move car

B

bluebsh

New member
Is this normal or not? I've gotten conflicting answers in the past and with little transmission knowledge I'm not sure what to expect.

I have a 2008 GP Base, when I put it on a flat surface and put the transmission into neutral it sits perfectly still when no brakes are applied and very quiet idle at about 500 RPM.

If I put the transmission into Drive from the same location the RPM will jump up to about 800 and the car will start going forward at 2-3 MPH.

I've have people in the past tell me that is weird, and people tell me that is normal.

I ask this again because I noticed that when I sit at a stop in drive it feels like the engine is fighting the brake and starts to sound like its trying to push and you have a noticeable increase in engine noise / vibration... if I drop into neutral at that moment it happens boom, silent and no feeling its trying to move.

My other car (chevy cruze) when put into drive sits perfectly still... I've only ever noticed this on my GP.

Is this normal for this car?
 


It's normal to have the car move in drive on a flat surface.

When you have the brake applied while is drive the torque converter is allowed to slip and let it stay still without moving and when you take your foot off the brake it that slip turns into a forward movement because nothing is holding it back.

That's the non fancy way of putting it. All regular automatic cars will do this. Some have a hill assist package will be keep the brakes applied for a few extra seconds to hold the car still but anything with a torque converter will move under it's own power on a flat surface.
 
Was he asking if the rpms jumping up is normal, or the car moving in drive? Of course all Automatics will crawl in drive at idle, even a cruze.

The rpm's jumping up when you put it in drive is something my GP does, which is not something most people would probably notice. I think the pcm opens the IAC a bit when putting it in gear because it knows the rpms will drop naturally. Try moving from park to neutral and watch the rpms go up just from that, without pressing the brake more than just enough to trigger the brake switch.
 
it's sort of normal. the 3800 makes enough torque at an idle to move the car forward.
there's a table in the PCM that sets idle RPM depending if you're in park/neutral or drive. When you shift into gear, it puts load on the engine. The PCM commands the idle air controller to open so the engine doesn't stall. Its weird the RPMs *jump* to 800. Typically the idle RPM in gear is a little lower than in park or neutral.
 
Moving in drive is normal, but it sounds like you're fighting something else from the way you described the issue. You shouldn't be fighting the car to keep it in place.

Can you feel the car jerk forward when you shift into drive?
 


in gear idle is higher then in park or neutral. sounds normal to me, every auto trans ive ever owned will move in gear with no gas.

no way your at 500 rpm either.

you idle at 725 rpm, in gear about 650. this is from a 05 tune, cant see a 08, but it cant be far off. stock tack is off most of the time, a t app scanner could tell you what its actually doing.
 
Clean your throttle body. It may have carbon buildup partially hiding the throttle open causing you to feel it pulling forward.
 
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