Quote:
Originally Posted by wheelhaus
I want to clarify this as it's a bit misleading... The gearbox does not have any special mechanism that locks you out of any gears, anytime, ever, it doesn't exist. The effect of the thick cold fluid however, prevents the synchros from generating the necessary friction to do their job effectively. This results in what feels like a lockout, but it's just the synchros unable to do their job.
Upshifting quickly and relatively firmly helps to ensure you catch the next gear as the revs drop. The thick cold fluid will slow the transmission internals down much quicker than normal when you clutch in. Downshifting is much more difficult as the synchros need to speed up the tranny. Double clutching is the best way to get the cold tranny to cooperate.
If you slow shift and the tranny internal RPM drops too far, it'll feel "locked out". Engage the clutch in neutral and blip the throttle a bit higher than it needs to be for the gear you want, and then quickly clutch-in and shift into it; should drop right in. (This is the essence of double clutching, as it bypasses the synchro's friction function and instead uses the engine to speed up the transmission internals before engaging a gear).
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The whole idea of the synchronizer system is to delay the system from sliding the locking ring down onto the gear you're selecting until everything is lined up. When the synchro system is working correctly it stops you from selecting a gear until the synchro and locking ring line up. The teeth on the synchro and locking ring are stuck pushing against each other on the ramp faces instead of sliding down next to each other and engaging that locking ring. That's what you feel when you're locked out of gear.
The gear stack is turning because you're moving. The input shaft may slow down after the clutch is disengaged, and at that point the synchros are doing what they would be doing on a downshift, they're not suddenly obsolete because the input shaft slowed down a little faster than normal.
What I said was quick and dirty, but misleading? I think that's a stretch.