I used to have a 1989 Opel Vectra where I skip - shifted from second to fourth without double - declutching, and I quickly learned that skip - shifting can cause noticeable
synchronizer wear in less than 10 000 km.
Yes, double - decluthing does save
some synchronizer wear but not all synchronizer wear.
@Lathejockey81 - you don't think
the synchronizers wear out?
Not exact matches
Likely to be a
worn 5th gear
synchronizer.
Double - clutching will, if done properly, eliminate any additional
wear of the
synchronizers and if the engine is running at just the right speed before you engage the clutch after the downshift, the clutch will not have to drag the engine up to speed.
The
synchronizers have a
wear material on them and can be shaped like a cone and once the speeds of the shafts match (through the gear ratio), then the output shaft is connected to the gear and everything is spinning and power can be applied by releasing the clutch pedal.
When shifting down due to other reasons such as needing acceleration when you have low RPMs, execute the double - declutching procedure to save the
synchronizers from extra
wear.
So if you leave the clutch pedal released, and if the engine power is such that no torque is being applied by the engine, there could in theory be less
wear on the
synchronizers when disengaging them by moving the shifter to neutral because you can artificially make that amount zero.
When skip - shifting up, execute the double - declutching procedure without pressing the gas pedal to save the
synchronizers from extra
wear.
Some answers correctly identified
wear of
synchronizers as a possible concern on manual transmission cars, but then they offered double - declutching as a solution.
There are three components of
wear I will consider: shift linkage, gear
synchronizers, and clutch throwout bearing.
Thus, there is some
wear on the
synchronizers unless the driver has magical ability to estimate how much to press the gas pedal.
The most common reason a manual transmission would jump out of gear is due to low or contaminated fluid,
worn synchronizers inside the transmission, or improperly adjusted shift linkage.
The «4 - 5 shift crunch» issue may well be a
worn synchronizer in the transmission.
Difficulty in engaging other gears could be
worn synchronizers as well, or transmission...
If the clutch is functioning and thus ruled out, and there is adequate gear oil in the transmission and the shift linkage is not faulty, then the likely cause is
worn synchronizers, hub gear and so forth.