Originally Posted by
DrJeremy28
I am sure this has been beaten like a dead horse and I did a search on this already BUT, can any SMG owners give me an honest opinion on your experience? I would like to pick up an E46 M3 (currently have a 330ci 5 speed), however I don't know if the almost double premium for a 6 speed is worth it. I understand the SMG can be problematic, but is it one of those things that people complain about because it is simply expensive to fix or is it truly a nightmare like some make it seem? To me, paying $10,000 for an SMG M3 vs $18,000 for a 5 speed leans me towards the SMG and saving the $ for "repairs". Anyone stories, advice, etc would be appreciated.
I own a 2004 M3, currently rebuilding the block with forged internals to handle ~800hp before the block needs sleeved, just got done at the machine shop. With the engine and tranny out, I opted to keep my SMG setup and simply relocate it. Here's my feedback on the SMG II experience with Getrag 6-speed tranny... (keep in mind, I also own a Mk6 GTI w/ Stage 2 boost, full intake & exhaust mods, 6SM):
-> The SMG, if you understand how to drive it correctly, will give you the best of both worlds IMO; the feeling of driving a manual transmission without the need to control the clutch. Do not expect it to drive like a DSG/dual clutch, or any of the new automatics that are super smooth. Many newer BMW owners prefer the smoothness of dual clutch or automatic; I much prefer the violent, visceral feel of the single clutch being actuated by the SMG computer. It feels extremely mechanical. Some folks like to change the sensitivity of the shifts, using the SMG shift mode button; some like it shifting with a pretty large window of delay, and only shifting quickly under specific conditions. I personally prefer to keep it in Shift Mode 5 or 6 (6th level is only available when you turn off TC), with the Sport mode button on at all times... how an ///M should be driven anyway, right? 
-> Rev matching is possible; I don't have my SMG tuned to the latest software revision yet, so I typically blip the gas upon downshifting, which causes the computer to slightly stall the actuation of the previous gear for proper rev matching. Upon dropping the tranny, I found the clutch was OE, pretty worn. I'm upgrading to a single mass flywheel and a new organic clutch disk, new pressure plate, so I'm certain the engagement of gears upon down shifting with rev match will be faster. Thus, rev matching is not automatic but still possible. I loved the auto rev match feature in my 2014 370z, that was an art!
-> Maintenance; to prevent overheating (one of the primary issues) I recommend to relocate the SMG unit itself away from the engine block OE position, to the passenger drug well bin. I purchased all parts needed for a relocation kit from Burkhart Engineering; SMG fluid reservoir, relocation hydraulic lines, relocation wiring harness, and mounting bracket that fits perfectly inside that drug well bin area (perfect spot for it, why didn't they make this the OE location for the unit?!); no more overheating issues, and optimal performing when you replace the electric pump motor (if your M3 has high mileage) and use Burkhart Engineering high performance SMG fluid (flows better than the OE Pentosin equiv). It will also free up a ton of room in that area of the block as if you didn't have SMG; except that your SMG unit will now be in a relocated area that keeps it completely away from the heat of the engine, and allows for very easy access for maintenance/repairs. Change your SMG fluid in the reservoir on regular intervals. Pray to god your solenoids aren't bad or leaking! Removal of the SMG unit from the stock position is a PITA; best to do it when you pull the motor for a rebuild, or if you're dropping the tranny for a clutch service/flywheel upgrade.
-> To make shifts feel less violent/more smooth, you can simply lift off the gas pedal each time you upshift. It will make the shifts feel less jerky/mechanical. Combine this with a lower shift mode, should feel almost as light as an automatic.
-> This is more rare, but still possible; I've seen where some SMG units have a failed pressure accumulator. This is a major problem, the SMG unit makes gear shifts using the hydraulic fluid at different pressure levels, up to 100psi. It's crucial that the SMG unit maintain appropriate pressure levels for gear shift actuation to occur quickly, smoothly, without error. I believe either the SMG computer or the DME itself will throw error codes based on accumulation pressure issues, if this is the case.
-> Be aware of how to properly drain/relieve the pressure in the lines and the accumulator of the SMG pump unit if you decide to remove it from the OE location, and relocate it. It is a high pressure system; failure to discharge will cause hydraulic fluid to go absolutely everywhere, you do NOT want to clean up this mess!
Don't get me wrong, I love the 6SM in my Golf GTI on Stage 2; super fun to manually throw into each gear with a high-boost turbo tune! But, I will be one of the few that actually prefer the M3 with the SMG transmission option. As stated, IMO it provides the best of both worlds to manual & auto; a Getrag 6-speed hooked up to a hydraulic pump, giving me the manual feel without needing to worry about constantly dealing with the clutch. The violent, visceral feeling of each shift banging into gear in shift mode 6 is just phenomenal. It also allows you to be a more efficient racer on the track also, you'll get better personal times around a circuit with SMG than 6 speed.
I think many haters hate on it simply because they've never driven one daily to a point of understanding how to properly drive one. Haters will also complain of the cost to maintenance/repair the unit; while I don't argue that it's expensive, it's not nearly as bad as it used to be. There are many companies now that provide separate components of the overall unit for fractions of the cost of a full unit replacement. There are many DIY guides showing how to maintenance the unit without having to take it fully apart or, as stated, simply replacing the entire unit outright. As you can tell, I highly recommend it myself, but ultimately you should test drive if you can, to get a feeling of what I'm talking about. If you get one, just relocate the damn thing into the drug well bin, replace the fluid with BE, upgrade the SMG software/tune, upgrade to a single mass flywheel, new clutch, you'll be solid! 
Last edited by twiceasfastasyo; 11-08-2019 at 12:05 PM.
2004 BMW e46 ///M3 S54 3.2L I6 NA ~360BHP RTD-6SM | Fully-rebuilt motor (forged lightweight rods & FSR pistons + rebalanced crank) & suspension, Conforti shark injector tune, aFe Stage 2 intake, Megan Racing catless SS headers (ceramic coated) + Status Gruppe sec 1 rasp elim + sec 2 un-resonated X-pipe + DNA motoring muffler (LOUD)
2013 BMW e82 135i ///M-Sport N55 3.0L I6 Twin-scroll Turbo ~380BHP DCT | MHD Stage 2+ tune, aFe Stage 2 intake, free-flow/catless down-pipe + unresonated mid sec + straight piped rear w/ titanium quad burnt tips (LOUD)
2012 VW GTI Mk6 2.0TSI EA888 2.0L I4 Turbo ~250BHP 6SM | Stratified tune, IE intake, hi-flow cat/downpipe, unresonated mid sec, stock gutted muffler (Sporty, civilized)
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