Quote:
Originally Posted by rc'Z
O-cha it is difficult to read, but read the first three words:
When shifting up on a non-synchroniser equipped vehicle, the clutch pedal is pressed, the throttle is released, and the gearbox is shifted into neutral. The clutch pedal is then released. As the engine idles with no load, the RPM will decrease until they are at a level suitable for shifting into the next gear. The driver then depresses the clutch again and shifts into the next gear. The whole manoeuvre can, with practice, take no more than a fraction of a second, and the result is a very smooth gear change.
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No BMW since the late 70s does not come equipped with synchronizers so this discussion is moot.
The problem here isn't that the 1st and 2nd gear ratios are too different. Synchronizers will ensure that the next selected gear is spinning at the same speed as the output shaft. There are two possibilities as to why there's a 1st to 2nd gear grind:
1: The 1st/2nd synchronizer is shot.
2: The input shaft is not completely disengaged when shifting.
It is entirely possible that the synchronizers on this particular transmission is defective, although if that were the case you'd hear a lot more than just the MZ4 drivers complaining about it since this particular model of ZF transmission is quite widely used. So that leaves the possibility of the problem being that the input shaft is not completely disengaged, meaning the clutch isn't completely disengaged when the shifting/grinding happened.
How much of this can be attributed to the CDV remains to be seen, but if you do a rapid 1st to 2nd gear shift right as you clutch in, it is entirely possible that the clutch hasn't fully disengaged yet before you put the car into 2nd gear, especially if the restriction in the CDV does not allow clutch fluid to flow through to the hydraulic TO bearing fork quickly enough to separate the pressure plate from the flywheel, resulting in the input shaft still receiving power from the engine.
I have yet to grind my 1st to 2nd shift in 2+ years of driving the MZ4 Coupe, then again I fully depress the clutch, wait a split second before I engage 2nd, even when I drive on the track (although on the track I would only make the 1-2 shift ONCE). Even with the CDV my first few events at the track shifting quickly between gears it has never been a problem.
(knock on wood)