Your M-Car Isn’t As Perfect As You Tell People It Is March 14, 2016 | 05:07 pm

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As the owner of an e46 M3 I reserve every right to trash my car as I see fit. Think of it as any guy affectionately complaining about his girlfriend/wife. Yeah I love the ol’ girl but nothing is without its faults.

First and foremost, I love my e46. The engine is visceral and raw, the chassis is nimble and responsive and the interior isn’t a half bad place to spend multiple hours in a row. There is no such thing as a entirely perfect car and the major fault I find in  my e46 is the Getrag 420G transmission.

I’ve always chalked up the clunkyness of the transmission to aging engine/tranny/subframe mounts. You could even add in giubo/u-joint or CSB as possible culprits as to why there was an ever present jerkyness to the clutch engagement. What I’ve come to accept is that this slop is inherent to this transmission and to indiscriminately generalize: all Getrag transmissions.

I’ve had the pleasure of driving multiple generations of BMWs and in this sampling there are both ZF and Getrag rowed specimens. One point to note is that all these cars are far from spring chickens. Most are far over the 100k mile mark and as such there is an expected ‘slop’ in all aspects  of the car. As a deeply mechanical person I refuse to compromise on the mechanical capabilities of my vehicles. If it shimmys/shakes/squeaks or does anything out of the ordinary I begin down the rabbit hole of systematic diagnostic. Typically it doesn’t take much to restore the feeling of crisp shits. Usually a dose of all new shift linkage and transmission mounts will remove most of the offending slop. [As a side note – solely replacing the shift bearing can work wonders as this is the fulcrum for the entire throw. Any play here will magnify itself more so than the assembly’s support bushings (side-to-side play). ]

But where do you turn when the linkage is fresh and the mounts are young, resilient and ready for years of abuse? If you turn to the internet for guidance you should find reference to the clutch delay valve (CDV) that is present on certain high horsepower variants e.g. the e46 M3 and e39 540i. The basic purpose of this device is to slow the uptake of the clutch by forcing the clutch slave cylinder’s brake fluid through an extremely small orifice. Preventing an instantaneous clutch engagement during a period where the engine is delivering high amounts of torque saves the driveline from potential shock. Instead, the clutch becomes the sacrificial lamb. I’ve removed these from both cars with little improvement to the overall engagement feel. It makes the engagement much more linear which allows for less jerky operation, especially in traffic.

CDV

CDV from e46 M3

Even after completing every item of the checklist you’re still left with a transmission that you essentially have to think about any time you’re shifting gears. Some may call this rewarding behavior…  “I like my Getrag 420G because it keeps me on my toes!”. I call it nuisance detail of an otherwise great car. Sure, it’s rewarding and feels great when you’re driving flat out i.e. time between gears is minimal, keeping your foot in the throttle a 1/4 second longer before lifting (call it a softcore flat shift). Come to think of it I’m sure this is where the SMG really shines (keeping shift time minimal to keep transmission loading constant). But when you’re poking along in traffic and only managing 1-2-1-2 shifts the constant jerking-around of your car’s under workings is frustrating. I never entirely made the connection until stepping back into my old e39 540i for the past couple months. This car shares the same transmission as the e46 M3, e39 M5 and several other variants which utilize either the M/S62 or S50B32 if you’re a lucky European.

My solution – drive my e36 M3! The lowly S52 was deemed too weak to deserve the robust Getrag 420G. Instead it received a buttery smooth ZF S5D-310/320Z depending on the year. I’m not one for modern BMWs (or car payments) but the ZF in the 135i is even buttery-er than the e36 M3. That was probably the nicest modern transmission I’ve had the pleasure of rowing.

So after my lengthy bitch session what’s my final conclusion? Not much sadly. Live with something long enough and you’ll inevitably find some fault, be it minor or major. In this case I’d call it minor and no where near enough to persuade me to part with my e46 M3 anytime soon.

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