smg gearbox problems?
Discussion
hi there, I'm thinking of buying another m3 e46, but this time possibly looking at one with the SMG gearbox, Ive heard they can be problematic and obviously expensive if they do go wrong, so, are the rumours true and if so do I avoid them and one more thing, if I do go ahead, is there anything to look out for while test driving? thanks
Andy
Andy
Rumours are true.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
Funnier because its so accurate!More random, there are a range of possible failures / mileage / age, some examples in this thread: http://www.pistonheads.com/gassing/topic.asp?t=689...
If it's the gearbox for you - have a slush fund to cover possible repairs, or just buy a manual - it's a lovely car to drive with three pedals.
If it's the gearbox for you - have a slush fund to cover possible repairs, or just buy a manual - it's a lovely car to drive with three pedals.
Most common faults are listed below, but very, very rarely properly diagnosed. The SMG is actually a relatively simple hydraulic actuation system, but very few techs ever take the time to learn how the system actually works to be able to use their brain to troubleshoot.
- SMG Pump Motor failure: It's a brushed DC motor in a sealed can. As the brushes wear, the carbon dust build up since it can't escape. This leads to low winding resistance, poor current handling, overheating, excessive brush wear. Oh yeah, and it has brushes so obviously they eventually wear out. £225 or so for parts, 3 hours labor.
- SMG pump relay: Constantly opening and shutting on an inductive load, therefor arcing and pitting the contacts. Pitting leads to high resistance, therefore higher voltage drop on the relay, less voltage available to the motor -> less torque and max pressure can't be reached. £5 part, 20 minutes labor.
- Clutch slave cylinder blowout: The o-ring on the piston seal blows out leaking hydraulic fluid all into the bell housing likely contaminating the clutch disc. In Getrag's infinite wisdom, they switched the fasteners for the slave cylinder to inside the bell housing for the first time ever on the GS7S47BG, so you have to remove the transmission from the car to replace the slave cylinder. £200 part, 4-5 hours labor.
- Clutch Position Sensor (PLCD) Failure: Still haven't nailed down the exact cause yet. Manifests as a red cog error and the very specific error codes 510D, 510E, and 4FA0. The transmission does not have to be removed for this, but does have to be pivoted down for access. £225 part, 2-3 hours labor.
- Of late, I have seen an increasing number of random errors due to the sensor strip wiring on the top of the hydraulic block exhibiting severe insulation degradation. Similarly to the recall issued in the US for the headlight and tail light wiring insulation failures, the sensor strip wiring shows a lot of copper. Caught early, I've seen liquid rubber insulation applied over the existing wiring and remedy the problem. Aside from that, the sensor strip has to be completely rewired which is possible, but you want it done by a competent automotive electrician, something neither BMW or most independents have. The only other options are to replace the upper actuator block with the sensor strip, these run about £250 on eBay. The upper block is not sold individually by BMW, so the entire hydraulic unit is the only option for around £2500.
- SMG accumulator loss of pressure: This is fairly rare, but happens occasionally. The accumulator loses its nitrogen charge and forces the pump motor to run far more often. The SMG module will usually pick up on this and store a code. £225 part, 2 hours labor.
- Galled guide tube / release bearing. The SMG III was introduced with the same metal guide bushing and metal -sleeved throwout bearing as every other BMW manual for years. In 2012, the throwout was redesigned to use a Delrin sleeve to prevent the galling associated with sliding metal on metal contact using grease in the presence of clutch wear dust. I've pulled apart two SMGs now with the revised part after 15-20k miles and it looks like this is a significant improvement as no stiction or wear has been noted. When having a clutch replaced, make sure the guide bushing is the new style.
- The obvious, clutch replacement. The clutch in the SMG, as with any other manual (automated or not) will wear out. However, this will be the default answer you are given for any single problem that a dealer diagnoses. AC not blowing cold? Must be a bad clutch. Left indicators not flashing? New clutch. This has gone on since the introduction of this car and is a shotgun approach at troubleshooting any problem with the SMG. It runs up the repair bill and although may fix the problem, it is often by accident. Many problems such as rough or slow shifting are solved by performing the very poorly named "SMG Adaptation" process. Well, when replacing the clutch, TIS requires teaching in the new clutch by performing "adaptation". Problem solved with a lot higher price tag.
- Flywheel: Recommended by everyone who wants to change your clutch. Sometimes warranted, sometimes not. If the flywheel has no hotspots, broken CPS teeth, or signs of damage, it's fine for reuse. BMW's position is that the dual mass flywheel can not be resurfaced, but I would argue that it just hasn't been done yet.
- SMG Pump Motor failure: It's a brushed DC motor in a sealed can. As the brushes wear, the carbon dust build up since it can't escape. This leads to low winding resistance, poor current handling, overheating, excessive brush wear. Oh yeah, and it has brushes so obviously they eventually wear out. £225 or so for parts, 3 hours labor.
- SMG pump relay: Constantly opening and shutting on an inductive load, therefor arcing and pitting the contacts. Pitting leads to high resistance, therefore higher voltage drop on the relay, less voltage available to the motor -> less torque and max pressure can't be reached. £5 part, 20 minutes labor.
- Clutch slave cylinder blowout: The o-ring on the piston seal blows out leaking hydraulic fluid all into the bell housing likely contaminating the clutch disc. In Getrag's infinite wisdom, they switched the fasteners for the slave cylinder to inside the bell housing for the first time ever on the GS7S47BG, so you have to remove the transmission from the car to replace the slave cylinder. £200 part, 4-5 hours labor.
- Clutch Position Sensor (PLCD) Failure: Still haven't nailed down the exact cause yet. Manifests as a red cog error and the very specific error codes 510D, 510E, and 4FA0. The transmission does not have to be removed for this, but does have to be pivoted down for access. £225 part, 2-3 hours labor.
- Of late, I have seen an increasing number of random errors due to the sensor strip wiring on the top of the hydraulic block exhibiting severe insulation degradation. Similarly to the recall issued in the US for the headlight and tail light wiring insulation failures, the sensor strip wiring shows a lot of copper. Caught early, I've seen liquid rubber insulation applied over the existing wiring and remedy the problem. Aside from that, the sensor strip has to be completely rewired which is possible, but you want it done by a competent automotive electrician, something neither BMW or most independents have. The only other options are to replace the upper actuator block with the sensor strip, these run about £250 on eBay. The upper block is not sold individually by BMW, so the entire hydraulic unit is the only option for around £2500.
- SMG accumulator loss of pressure: This is fairly rare, but happens occasionally. The accumulator loses its nitrogen charge and forces the pump motor to run far more often. The SMG module will usually pick up on this and store a code. £225 part, 2 hours labor.
- Galled guide tube / release bearing. The SMG III was introduced with the same metal guide bushing and metal -sleeved throwout bearing as every other BMW manual for years. In 2012, the throwout was redesigned to use a Delrin sleeve to prevent the galling associated with sliding metal on metal contact using grease in the presence of clutch wear dust. I've pulled apart two SMGs now with the revised part after 15-20k miles and it looks like this is a significant improvement as no stiction or wear has been noted. When having a clutch replaced, make sure the guide bushing is the new style.
- The obvious, clutch replacement. The clutch in the SMG, as with any other manual (automated or not) will wear out. However, this will be the default answer you are given for any single problem that a dealer diagnoses. AC not blowing cold? Must be a bad clutch. Left indicators not flashing? New clutch. This has gone on since the introduction of this car and is a shotgun approach at troubleshooting any problem with the SMG. It runs up the repair bill and although may fix the problem, it is often by accident. Many problems such as rough or slow shifting are solved by performing the very poorly named "SMG Adaptation" process. Well, when replacing the clutch, TIS requires teaching in the new clutch by performing "adaptation". Problem solved with a lot higher price tag.
- Flywheel: Recommended by everyone who wants to change your clutch. Sometimes warranted, sometimes not. If the flywheel has no hotspots, broken CPS teeth, or signs of damage, it's fine for reuse. BMW's position is that the dual mass flywheel can not be resurfaced, but I would argue that it just hasn't been done yet.
sim16v said:
Rumours are true.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
ok, difficult decision for me then, are they common faults or are you more unlucky if they do go wrong? all cars have their issues but on the whole most cars are quite reliable these days, for example Subaru impreza's are among the most reliable cars you can buy and even they have their 'common' faults
M3John said:
sim16v said:
Rumours are true.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
Easier option is to just buy a manual and get a friend to sit in the back and hit you on the back of your head with a piece of wood every time you change gear.
It'll give the same effect as SMG.
They are brilliant when they work, but have various issues that are expensive when they go wrong.
Have since driven several smg's and I'm glad I stayed with 3 pedals.
Test drove a few manuals and the long throw did not feel sporty enough for me. Ended up buying SMG which to be fair did take best part of a year to get used to. Keeping your hands on the wheel on the twisties is sublime. I run on S4 with manual gear changes and they're as smooth as any manual car. If I should ever drive in auto I use s2 to smoothen the change.
Bought the car under 50k seven years ago and it's just gone over 120k with no SMG issues. Thats a bummer really as I have been paying £80 a month in warranty because the forums told me it would all go wrong!
Bought the car under 50k seven years ago and it's just gone over 120k with no SMG issues. Thats a bummer really as I have been paying £80 a month in warranty because the forums told me it would all go wrong!
jcolley said:
Most common faults are listed below, but very, very rarely properly diagnosed. The SMG is actually a relatively simple hydraulic actuation system, but very few techs ever take the time to learn how the system actually works to be able to use their brain to troubleshoot.
- SMG Pump Motor failure: It's a brushed DC motor in a sealed can. As the brushes wear, the carbon dust build up since it can't escape. This leads to low winding resistance, poor current handling, overheating, excessive brush wear. Oh yeah, and it has brushes so obviously they eventually wear out. £225 or so for parts, 3 hours labor.
- SMG pump relay: Constantly opening and shutting on an inductive load, therefor arcing and pitting the contacts. Pitting leads to high resistance, therefore higher voltage drop on the relay, less voltage available to the motor -> less torque and max pressure can't be reached. £5 part, 20 minutes labor.
- Clutch slave cylinder blowout: The o-ring on the piston seal blows out leaking hydraulic fluid all into the bell housing likely contaminating the clutch disc. In Getrag's infinite wisdom, they switched the fasteners for the slave cylinder to inside the bell housing for the first time ever on the GS7S47BG, so you have to remove the transmission from the car to replace the slave cylinder. £200 part, 4-5 hours labor.
- Clutch Position Sensor (PLCD) Failure: Still haven't nailed down the exact cause yet. Manifests as a red cog error and the very specific error codes 510D, 510E, and 4FA0. The transmission does not have to be removed for this, but does have to be pivoted down for access. £225 part, 2-3 hours labor.
- Of late, I have seen an increasing number of random errors due to the sensor strip wiring on the top of the hydraulic block exhibiting severe insulation degradation. Similarly to the recall issued in the US for the headlight and tail light wiring insulation failures, the sensor strip wiring shows a lot of copper. Caught early, I've seen liquid rubber insulation applied over the existing wiring and remedy the problem. Aside from that, the sensor strip has to be completely rewired which is possible, but you want it done by a competent automotive electrician, something neither BMW or most independents have. The only other options are to replace the upper actuator block with the sensor strip, these run about £250 on eBay. The upper block is not sold individually by BMW, so the entire hydraulic unit is the only option for around £2500.
- SMG accumulator loss of pressure: This is fairly rare, but happens occasionally. The accumulator loses its nitrogen charge and forces the pump motor to run far more often. The SMG module will usually pick up on this and store a code. £225 part, 2 hours labor.
- Galled guide tube / release bearing. The SMG III was introduced with the same metal guide bushing and metal -sleeved throwout bearing as every other BMW manual for years. In 2012, the throwout was redesigned to use a Delrin sleeve to prevent the galling associated with sliding metal on metal contact using grease in the presence of clutch wear dust. I've pulled apart two SMGs now with the revised part after 15-20k miles and it looks like this is a significant improvement as no stiction or wear has been noted. When having a clutch replaced, make sure the guide bushing is the new style.
- The obvious, clutch replacement. The clutch in the SMG, as with any other manual (automated or not) will wear out. However, this will be the default answer you are given for any single problem that a dealer diagnoses. AC not blowing cold? Must be a bad clutch. Left indicators not flashing? New clutch. This has gone on since the introduction of this car and is a shotgun approach at troubleshooting any problem with the SMG. It runs up the repair bill and although may fix the problem, it is often by accident. Many problems such as rough or slow shifting are solved by performing the very poorly named "SMG Adaptation" process. Well, when replacing the clutch, TIS requires teaching in the new clutch by performing "adaptation". Problem solved with a lot higher price tag.
- Flywheel: Recommended by everyone who wants to change your clutch. Sometimes warranted, sometimes not. If the flywheel has no hotspots, broken CPS teeth, or signs of damage, it's fine for reuse. BMW's position is that the dual mass flywheel can not be resurfaced, but I would argue that it just hasn't been done yet.
That is very useful indeed - thank you! I have an SMG E46 M3 and I absolutely love it. There's nothing quite like zapping up through the gears on a slip road on to a motorway - I still love it. But these cars are getting on a bit now and problems are inevitable. I'm just glad to hear that the the SMG system generally seems to drop into neutral before it turns up its toes. Getting it out of the garage whilst stuck in 1st gear would be, well.....interesting.- SMG Pump Motor failure: It's a brushed DC motor in a sealed can. As the brushes wear, the carbon dust build up since it can't escape. This leads to low winding resistance, poor current handling, overheating, excessive brush wear. Oh yeah, and it has brushes so obviously they eventually wear out. £225 or so for parts, 3 hours labor.
- SMG pump relay: Constantly opening and shutting on an inductive load, therefor arcing and pitting the contacts. Pitting leads to high resistance, therefore higher voltage drop on the relay, less voltage available to the motor -> less torque and max pressure can't be reached. £5 part, 20 minutes labor.
- Clutch slave cylinder blowout: The o-ring on the piston seal blows out leaking hydraulic fluid all into the bell housing likely contaminating the clutch disc. In Getrag's infinite wisdom, they switched the fasteners for the slave cylinder to inside the bell housing for the first time ever on the GS7S47BG, so you have to remove the transmission from the car to replace the slave cylinder. £200 part, 4-5 hours labor.
- Clutch Position Sensor (PLCD) Failure: Still haven't nailed down the exact cause yet. Manifests as a red cog error and the very specific error codes 510D, 510E, and 4FA0. The transmission does not have to be removed for this, but does have to be pivoted down for access. £225 part, 2-3 hours labor.
- Of late, I have seen an increasing number of random errors due to the sensor strip wiring on the top of the hydraulic block exhibiting severe insulation degradation. Similarly to the recall issued in the US for the headlight and tail light wiring insulation failures, the sensor strip wiring shows a lot of copper. Caught early, I've seen liquid rubber insulation applied over the existing wiring and remedy the problem. Aside from that, the sensor strip has to be completely rewired which is possible, but you want it done by a competent automotive electrician, something neither BMW or most independents have. The only other options are to replace the upper actuator block with the sensor strip, these run about £250 on eBay. The upper block is not sold individually by BMW, so the entire hydraulic unit is the only option for around £2500.
- SMG accumulator loss of pressure: This is fairly rare, but happens occasionally. The accumulator loses its nitrogen charge and forces the pump motor to run far more often. The SMG module will usually pick up on this and store a code. £225 part, 2 hours labor.
- Galled guide tube / release bearing. The SMG III was introduced with the same metal guide bushing and metal -sleeved throwout bearing as every other BMW manual for years. In 2012, the throwout was redesigned to use a Delrin sleeve to prevent the galling associated with sliding metal on metal contact using grease in the presence of clutch wear dust. I've pulled apart two SMGs now with the revised part after 15-20k miles and it looks like this is a significant improvement as no stiction or wear has been noted. When having a clutch replaced, make sure the guide bushing is the new style.
- The obvious, clutch replacement. The clutch in the SMG, as with any other manual (automated or not) will wear out. However, this will be the default answer you are given for any single problem that a dealer diagnoses. AC not blowing cold? Must be a bad clutch. Left indicators not flashing? New clutch. This has gone on since the introduction of this car and is a shotgun approach at troubleshooting any problem with the SMG. It runs up the repair bill and although may fix the problem, it is often by accident. Many problems such as rough or slow shifting are solved by performing the very poorly named "SMG Adaptation" process. Well, when replacing the clutch, TIS requires teaching in the new clutch by performing "adaptation". Problem solved with a lot higher price tag.
- Flywheel: Recommended by everyone who wants to change your clutch. Sometimes warranted, sometimes not. If the flywheel has no hotspots, broken CPS teeth, or signs of damage, it's fine for reuse. BMW's position is that the dual mass flywheel can not be resurfaced, but I would argue that it just hasn't been done yet.
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