# SMG Trans jerking on acceleration...HELP!



## Sunshine (Jan 14, 2004)

I have an '03 M3 with the SMG transmission. When I'm in automatic mode, sometimes the car starts jerking back and forth when I start accelerating. The harder I press on the accelerator, the more violently the car bucks. The only way to stop this is to release the accelerator. This is not a good solution when I am pulling into traffic...

The dealer cannot reproduce this problem, because it does not occur all the time. Can anyone tell me what is causing this problem before I get killed by oncoming traffic?


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## bozo (Dec 14, 2003)

I have an '03 smg and I've made the car do jerking thing. Seemed to me once I spent some time driving it, the car didn't do it any more. I also loaned it to a friend of mine and she made the car jerk and didn't like it one bit. She did learn not to make it happen too. So all I'm saying I know of the jerking and mine dosen't do it for me anymore, just for some others who haven't driven it before.


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## Bruce (Dec 24, 2001)

I have heard....
Some people assume that you don't have to know how to drive a stick to drive an SMG, but to drive it smoothly you do. Have you ever driven a manual before? You can't just mash the gas and expect it to be smooth.


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## TGray5 (Jan 22, 2002)

How long have you had your car? There IS a learning curve with SMG. Also I suggest not-activating sport mode as that makes the throttle even more sensitive. Essentially what's happening is that your foot is creating the jerking motion as a result of the firm ride in the car...for example going over speed bumps, etc. Your brain and foot need to get used to the sensitivity of the pedal and to keeping your foot in a constant position despite movement of the car over bumps.


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## Seneca (Feb 13, 2003)

I had this problem also with the last M3 SMG II that I drove, but also found that it was much smoother without the Sport mode turned on. It also helps to keep the transmission on the lower settings and be VERY tentative with the throttle.


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## Sunshine (Jan 14, 2004)

I currently have 5000 miles on my car. I usually do not have it in sport mode, and it doesn't seem to care if I am gentle or aggressive on the accelerator. It's never happened in manual mode.


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## Sunshine (Jan 14, 2004)

StahlGrauM3 said:


> How long have you had your car? There IS a learning curve with SMG. Also I suggest not-activating sport mode as that makes the throttle even more sensitive. Essentially what's happening is that your foot is creating the jerking motion as a result of the firm ride in the car...for example going over speed bumps, etc. Your brain and foot need to get used to the sensitivity of the pedal and to keeping your foot in a constant position despite movement of the car over bumps.


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## Sunshine (Jan 14, 2004)

It only happens when I accelerate from a stopped position.


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## armstd (Jan 2, 2004)

Think about it this way. When you hit the gas, SMG lets out the clutch. When you let off the gas, SMG puts in the clutch.

No imagine taking a regular manual transmission, and pushing the clutch pedal in and out in quick succession while giving it gas at the same time. Same result.

As everyone else said...you *have* to get used to the throttle on this car. It's extremely sensitive, and because of SMG, the car does a lot more than just slow down when you let off the gas. In that way it is different from every other car you've ever driven.

The good news is, it's not a problem with your car. It's not an ideal design, and maybe you could call it a problem with the M3/SMG, but it's not that your car is malfunctioning. The more you get used to the car, the less the "washer cycle" will happen.

-Daver


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## Desertnate (Mar 11, 2002)

armstd said:


> Think about it this way. When you hit the gas, SMG lets out the clutch. When you let off the gas, SMG puts in the clutch.
> 
> No imagine taking a regular manual transmission, and pushing the clutch pedal in and out in quick succession while giving it gas at the same time. Same result.
> 
> ...


As you read the above quote Sunshine, remember that even when in automatic mode you are not driving a car with an automatic transmission. I have heard of similar complaints before from SMG owners. The biggest aid was for those folks to realize that they did not have an automatic transmission like in other cars they had driven/owned, but acutally a manual transmission that had the clutch pedal stolen and some computer logic put in its place.

Don't know if that helps or not.


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## Pinecone (Apr 3, 2002)

armstd said:


> Think about it this way. When you hit the gas, SMG lets out the clutch. When you let off the gas, SMG puts in the clutch.
> 
> No imagine taking a regular manual transmission, and pushing the clutch pedal in and out in quick succession while giving it gas at the same time. Same result.


NOT true, from what youare saying is an SMG would not engine brake, and it DOES, most definately.

And the jerking also happens with manuals, but there you CAN push in teh clutch pedal and stop it.


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## Pinecone (Apr 3, 2002)

Sunshine said:


> I have an '03 M3 with the SMG transmission. When I'm in automatic mode, sometimes the car starts jerking back and forth when I start accelerating. The harder I press on the accelerator, the more violently the car bucks. The only way to stop this is to release the accelerator. This is not a good solution when I am pulling into traffic...
> 
> The dealer cannot reproduce this problem, because it does not occur all the time. Can anyone tell me what is causing this problem before I get killed by oncoming traffic?


Typically you will find that this happens after being stopped for a while. What happens is after several seconds the SMG shifts into Neutral. When you want to go, you step on the gas, and the trans has to shift back into first. So it sits there. So you push harder on teh gas, and the tranny finsihes shifting, about the time you push even more on the gas. Now the things starts to take off, but due to teh acceleration you end up in an occilation loop. The acceleration pulls your foot off the pedal, so you try to push harder, but at the same time, since your foot is coming off the pedal, the cars slows, making your foot move forward on its own added pedal pressure, at the same time the order from your brain says to push harder, you your brain says let off, but the acceleration lets off for you about the time your brain says to let off, etc etc etc, bucking down the road.

The fix, once it happens it to either floor it, or let off the gas. Either will work, however flooring an E46 M3 can lead to RAPID acceleration and a ticket. So letting off the gas is a good move.

To prevent it, you have to understand what is happening and have patience. Understand that if you have stopped for a while, the trans takes time to shift into gear and start moving. Relax. You can also roll your foot slightly to the right and push a little on the gas just before you want to go. This will cause the trans to shift into gear. Or tap the stick into neutral and back into gear. The idea is to reduce the lag of the car having to get back into gear.

Remember, as others have said, this is a MANUAL transmission, with a sort of auto mode. It is NOT an automatic transmission.


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## cchan (Sep 19, 2002)

One other "fix" if you get into the oscillation loop -- upshift a gear from 1st to 2nd... SMG will disengage the clutch to upshift, so the oscillation should stop. You'll be in the 2nd gear early and at low RPMs, but there's more than enough low end torque to keep moving through an intersection at a functional pace instead of having to back off the gas with traffic behind you.


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## Sunshine (Jan 14, 2004)

Thanks for the input all. I found out how to reset the clutch engagement and that has appeared to have helped. If anyone is interested, this is how you do it:

1. At 20 mph or greater, shift the car into neutral
2. While in neutral, pull back on both paddles for a good 3 seconds
3. Then put the car back into gear.

There is no indication of the clutch being reset, but should notice a difference if done correctly.


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## mquetel (Jan 30, 2003)

Pinecone said:


> NOT true, from what youare saying is an SMG would not engine brake, and it DOES, most definately.
> 
> And the jerking also happens with manuals, but there you CAN push in teh clutch pedal and stop it.


Or ease off the throttle...


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## PowerM (Feb 13, 2004)

Hey,
I'm a huge fan of the SMG transmition and I have the same problem (well I learned to avoid it). It happens in automatic mode when the car is shifting from second to first and you begin to accelerate. Try that and that will trigger the "bucking" so you can show your dealer.


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## PowerM (Feb 13, 2004)

sorry about the pictures!!!!


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