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BANG when starting in 1st... something I'm doing wrong?

7K views 38 replies 17 participants last post by  Major Cheese 
#1 ·
Hello all,

I'm new to this car, and SMG in general. So, maybe it's me, but every once in a while, say once a week at least, I get a bang when starting off that feels like the "rear ended feeling" people on here describe. It's always from a dead stop, and always when I am just driving off normally (not red-light drag racing). Feels like when you're learning to drive stick and you let the clutch out too fast!

No warnings, no red/yellow cogs of death, just the occasional rear ended feeling when starting off in first from a stop.

Anything I'm doing wrong? Can I control this at all?

Thanks!!

Steve
 
#2 ·
Are you applying the brake at the red light? You have to keep your foot on the brake the whole time then when you release the brakes the car will assume you're getting ready to take off so it'll engage the gear like normal without a bang. Otherwise it'll just dump the clutch if you don't.
 
#3 ·
Interesting.... i have the same issue the OP stated above, and i do tend to take my foot off the brake when at a stop light. Sometimes it feels like the rear end is going to fall off it is so violent. Since i think the clutch is close to the end of life (shuddering in 1st and 2nd takeoff) i thought it was a clutch engagement problem.i will keep an eye on this, thanks for the heads up.
 
#5 ·
I get the bang once in awhile but it's my fault as I take my foot off the brake and let the car drop into neutral or disengage completely out of gear.
 
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#7 ·
Holy sh*t, thanks guys. I'll definitely give this a try. I never read that anywhere, and I've been through several hundred pages of tech pubs that were posted in the stickys somewhere. That is absolutely crazy, but it makes sense that with the brake release, the clutch has time to predict a request for engagement, otherwise it has no idea when you plan on hitting the gas.

Will do this and see what happens. I'll make sure to engage the brakes before setting off, if I do have to sit at a light for extended periods of time. Every time its happened, it was always while waiting for a light to change, and most likely with foot off the brake (again, a habit carried over from manual transmission driving).

Will keep you all posted.
 
#9 ·
Yep, I'll confirm the same here. I was hoping it'd go away after the clutch job but even with a new clutch, flywheel, SMG pump, slave cylinder and misc other parts it still does this if I take my foot off the brake for more than ~10 seconds at a light. Oh well, I'll just call it a "personality" trait. hiha
 
#10 ·
respectfully i disagree with the advice given so far. if you have a hard bang...a violent one like someone slammed into your rear end...its not a foot-off-the-brake issue.

its a larger issue. i dealt with it on my car for months until it got so bad that my transmission went out completely. my issue was a tale tale sign of a clutch position sensor that was on its way out and ultimately failed.

there was no coding or clutch adaptations that could fix it. once it went, it had to be replaced. otherwise with increasing frequency if i didnt FEATHER the gas pedal from a dead stop until the clutch was fully engaged, it would BANG into gear violently.

ultimately i replaced everything connected to it: the clutch position sensor, the throw out bearing / clutch release bearing (which was totally shot btw), new clutch, new flywheel, SMG fluid flush, EURO smg flash and new adaptations.

now it shifts perfectly again. i wouldnt try to write this off as a braking issue....its far more complex than that if you are indeed experiencing slamming into gear. good luck out there fellas...
 
#20 ·
For what it's worth I think you're describing a different issue. I had my CPS replaced with my clutch/flywheel and I still get this "bang" if I sit with my foot off the brake at a light for an extended period and then hit the gas without touching the brake first. It doesn't always happen, and it isn't so bad that it feels like I got rear-ended, but it's a significant "thunk". This is the only time it ever happens, taking off from a stop normally is smooth and I never get any bangs or anything shifting between gears.
 
#11 ·
^^ Agree with this guy. Let me be sure to clarify, its a jolt but not a real severe one that some describe. It just doesn't feel like the usual set-off. Easy enough in my case to sort out, because if it still happens after I modify my technique, then it is another issue like mentioned above. It ONLY happens when setting off in first from a dead stop, and I DO sit with my foot off the brake, carried over from normal MT driving habits. It NEVER happens in between gears and I have no other abnormalities noted with the shifting.

Just to be clear, in case someone is having something else going on with theirs...
 
#15 · (Edited)
First try resetting your SMG by rolling at about 20mph and holding both paddles in for about 5 seconds (it's been a while so I may be incorrect about how long you hold the paddles in). If that doesn't fix your problem I would assume it is your clutch position sensor. I had the same issue and thats what it turned out to be. Got it replaced and haven't had any problems with that since. Replaced at 64k, now at 69k.

EDIT: Before I got my CPS replaced, there would be times where there would be a perfect transition between stop and go in first gear, and other time where I felt like I was rear-ended by a vehicle going about 5mph behind me. Eventually it go so bad that the CPS failed, and the car would completely stall every time. CPS replaced and everything was perfect.
 
#17 ·
yup, sounds like we had the same exact issue. unfortunately for me....i replaced a ton of parts including clutch and flywheel before realizing it was the CPS. probably could have saved myself an easy $2k but oh well, the clutch and flywheel are brand new now. ive only put like 1200 miles on the entire system since it was replaced a few months back in the spring or so...

OP good luck with the diagnosis!
 
#18 ·
Copied my response from another thread, since there are about 80-billion threads on this issue:

First off, the SMG reset is 2 seconds, not 5, 10, 8 or whatever it is people say. I don't know how the number has evolved so much over the years - the manual clearly states 2 seconds. Second off, this does NOT reset the SMG. It's not a fancy fix-all reset - all it does is calibrate the rollout of the tires so the torque calculations the SMG performs are accurate. You do this reset whenever you get new tires put on the car.

A proper SMG "reset" is really called SMG adaptation and it resets the clutch engagement and shift gate calibration of the car, and must be done with the car hooked up to the proper software. However, this is someone you will want to look into and have the adaptation done when the car is nice and hot and you've gone through the gears. Not with a cold clutch or else everything will be off. If I remember right, doing this also clears out any and all "learning" the SMG has done to get to know you as a driver. The SMG system tries to learn the way you drive so that it drives better with you. It watches how you drives and adapts. Right now, it remembers whoever used to own the car. It has to learn you. (FYI - it has one profile per key, so make sure you are always using the same key, and if someone else frequently drives the car, let them have the other key and let these keys be "assigned" as everything from seat position and radio stations to climate control preferences is also unique to each key).

Lastly, you'll want to have Euro-SMG coding put on your car as soon as you can. Because US-Spec cars had the free maintenance, BMW gave us a different SMG programming that sacrificed shift comfort for clutch preservation to avoid having to install a new clutch. Long story short, it makes the car shift like crap. Once you get the Euro software on there the car will drive much better and you will totally say this is how it should have come from the factory (and it did! - just not in the US lol).

Finally, now that you know all that, I will say that it takes some getting used to (it's a learning curve for both you and the car), and it also helps for you to understand how the SMG works and thus its limitations and your expectations. Right now I'm talking about D mode.

The SMG is NOT an automatic. Automatics have it much easier since everything they do is smooth - why? Because a torque converter has very little back-torque transfer under normal conditions. The SMG is a clutched manual, and thus it has full back-torque transfer so you feel every slip, lurch, and clunk from those clutch engagements. This about how it works - the SMG is basically a guy with a clutch on one foot and a gear shifter in his hand, watch you apple gas and throttle. He looks at engine RPM, throttle input, and current gear to determine what to do. The SMG WILL NOT UPSHIFT unless you are giving it some sort of throttle. You cannot rev it out the 7K, then completely cut throttle and expect it to upshift. It will not do that. I think this is the biggest difference between it and an automatic in terms of programming.

The Drivelogic mode you are in (D1 - D5, or otherwise, D mode, however many bars are lit - NOT the gear indicator to the left of "D" on the instrument cluster) determines the base aggressiveness of the shift program. D1 will will generally be very conservative and shift as early as possible. D5 will try to hold gears and will wait a long time to upshift. You must choose the settings to your driving style. If you are on the autobahn and just slaughtering traffic, D5 might be great - it always downshifts aggressively upon strong throttle application and shifts late and generally shifts quickly. Choose D5 when you're creeping in traffic and you'll want to get out and start kicking the car. In a general sense though, don't use D1 as it starts in 2nd gear and fries your clutch.

My personal preference is D2. I use it in conjunction with P500 (not P500S). D2 shifts relatively early and is smooth, but having it in P500 helps with getting some torque out of the motor. P400 is far too desensitized, in my opinion.

When you eventually get the feel of the car, you'll be able to "tell it to shift" even with D. I now will roll into the throttle and then lift slightly when I want the car to shift. It does so perfectly even in D mode. Also, this means that YOU are still in command of the shift timing of the car even with it in D (you are just using your foot rather than your paddles). I think this is one of the biggest frustrations of SMG, is the car being in the middle of a shift when you need to make a move. This helps alleviate that problem.

Now, for when you are driving in manual mode, by all means feel the car like a manual. Upshift whenever you feel it's the right time. When I drive with this intent the car never gets shifted before 5K, and the car is almost always about 3500RPM. It just feels more alive and ready. Not practical for mileage, no, but I leave it in D to get better mileage. Second, let the car do the work for you. The car will not let you downshift to 1st gear at 80mph on the highway, so if you need max acceleration, just pull the downshift paddle like 10 times and mash your foot once you year the RPMs jump up to the characteristically correct sound. You'll get your acceleration without the BS of having to do quick math to see how many gears you need to go down.

Lastly, and this is really just getting used to the characteristic of an S85, is that the S85 is naturally a high revving motor. It likes to be revved out. In your E39 I'm sure you were used to using that great bottom end and broad mid range to leisurely pull the car everywhere - the S85 is not like that. The S85 wants you to use its rev range. That is where its power comes from. From 3K+ the car wakes up from 6K+ the car just enters rabies mode and all hell breaks loose in the best way possible.

I know this was a long post but I hope it helps you get to know your SMG better. Personally, I love the SMG and think it's an amazing transmission that helps you get the most out of the S85. When the SMG is working correctly, it's amazing how smooth it can be, and at the same time, how brutal it can be in S6 when you're going through the gears.
 
#19 ·
+1 all these years of driving this car and still learning new things... amazing!
 
#22 ·
Well, it's just about been a week since I posted this, and after modifying my driving technique.......



THE CLUNK IS GONE. DONE. FINISHED. Hopefully never to return!! Havn't had a hard start in any condition, any shift setting, any mode what so ever. Again many thanks. Hopefully my noob question has also helped others lol
 
#23 ·
Well, it's just about been a week since I posted this, and after modifying my driving technique.......



THE CLUNK IS GONE. DONE. FINISHED. Hopefully never to return!! Havn't had a hard start in any condition, any shift setting, any mode what so ever. Again many thanks. Hopefully my noob question has also helped others lol
Congrats!! I did the same test the last few weeks and confirmed the same thing LOL.
 
#24 ·
There is no need to keep foot on the brake. C'mon... All you have to do it is to click down paddle or push shift knob forward before you run and then clutch will be released properly. No Bang. I'll do it daily. Other technique is to press brake a little just before you run.
Another tip: push brake and clikc shift up, you got 2nd gear. Ready to go...

So in general, when I start from dead stop, before I push trothle I click down paddle and it works as it was designed...
 
#25 · (Edited)
Why would you want to start out in 2nd, trying to wear your clutch prematurely?

I'll have to try the downshift before moving thing, first time I've heard that one. But really, it's not that hard to just leave your foot on the brake (nor is it a big deal IMO, just a habit to get into).
 
#26 · (Edited)
It's a trick how to put car in the 2nd gear. You may want it - winter, slippery road, etc ? In D1, car starts from 2nd too.

For me, it's a myth that starting from 2nd is wearing clutch prematurely. It's nothing comparing to changing gears during max load at 8k rpm using 500 horse power. It's not a baby.

Keeping foot on brake - not good at all, especially when you drive fast and have hot brakes.
 
#27 ·
Interesting to note the click of the downshift lever also "readies" the clutch release mechanism. I wouldn't really advise making a regular habit of starting off in 2nd... to be honest I leave my shift speed in level 5, for minimal slip of the clutch. You sacrifice a slight bit of smoothness, but you are overall extending the life of the clutch. Mine is at 75,000 miles, so the previous owner (I'm the 2nd) must also have understood this. Did a little research, and the guy who had my car previously has quite a collection... Carrera GT, a few F-cars. I think he was used to driving a car with this sort of transmission which is interesting that many on here are only getting 50-60K out of a clutch (?).
 
#28 · (Edited)
In europe, the smg software auto starts in 2nd gear or drivelogic speed 1 compared in other parts of the world where it starts in drivelogic 3/ 1st gear.

The car is designed around keeping your foot on the brake during stop lights and traffic situations. And its no myth that starting off in 2nd gear has more clutch wear then starting off in first, how much is not measurable. BMW really was sensitive with markets like the USA, with the basically no launch control and starting off in first gear as default to try, and limit clutch wear as much as possible compared to Europe.

Anyways, foot on brake during stops. Easy/simple solution
 
#30 ·
I agree. I don't know why people make it more complicated than it has to be. Also a note if you are hard on the brakes and don't want to apply them when you're at a standstill just throw the car in neutral this of course if is you are on a flat surface. Applying the emergency brake while the rotors are very hot (track driving for example) it will act as a heat sink and warp the rotors. Seen it on an M6 when I was at MFest.

My buddy's 430 Scuderia the transmission is the same way you apply the brakes at the stoplight the whole time it is designed that way.
 
#29 ·
Good thing I read this thread. I would get the same thud and it was annoying. I didn't hold the break at stop signs, mainly because I would treat the car like a true manual, especially if I get to do a bit of roll back on a slight slope.

Well car is in storage now but I guess I'll try that come spring...
 
#31 ·
I love it when people argue of a very simple fix.
 
#32 ·
The adjustment of driving style really works guys, i clicked shifter before i took off or tapped brakes, no thud all weekend. After i got home i took wife to the store and purposefully tried to replicate, got a thud at the last stop sign, thanks to all on the board for a really easy fix.
 
#35 ·
That is fine, just make sure to hit the brake and then proceed to get on the throttle, i do it all the time... Or if you roll back, get on the gas within 5-10 seconds, or the thud will occur if you wait longer then that and get on the gas.

Now if everyone did driver mod with the SMG, i think alot more SMG's would be in great shape.. Hold brake, no thuds, no full throttle (burnout mode) starts from a stop, no LC, no riding the clutch, and first gear starts :)
 
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