Question: Short shifter bad for transmission syncros?
10-20-2005, 12:36 PM
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Question: Short shifter bad for transmission syncros?
<ul><li><a href="http://www.dieselgeek.com/a_word_about_transmissions.php">http://www.dieselgeek.com/a_word_about_transmissions.php</a</li></ul>
10-20-2005, 01:42 PM
#2
It's not necessarily the short shifter but the timing alloted for one side of the gear shafts to
reach neutral so that the gears they are connected to, can be engaged by a spinning side because they are spun by the wheels.
The only reason for not being able to shift is because the speed of the engaging gears connected to the engine is not synchronous to the speed of the shafts eventually spun by the driveshaft (of a moving car).
When the clutch is depressed, the input shaft of the transmission is allowed to free wheel. This allows the gears connected to the input shaft to freely engage to the spinning shafts of a moving car.
The engaging is done by "couplers" with teeth (not gears) to match teeth with the spinning gears. These couplers contain "synchros". The synchros as dieselgeek describe, allow this smooth transition by having the couplers applying friction to the gears connected to the free wheeling input shaft, have them match speed and then eventually hard engage with their teeth.
The grinding noise is because the shafts are not at matching speeds yet and the clutch is released too soon so the engine speed started driving the input shaft, which may not be in synchronous relationship with the output shaft. It's the teeth of the couplers that grind and eventually wear out, then shifting becomes a pain.
So, add the equation of a short shifter, wherein with the same arm speed, the coupler engagement is faster and sooner. If you are slow with your left foot, then you might not be fully depressing the clutch as you move to engage the next gear. This will eventually cause grinding and damaging of the couplers teeth.
The other thing is you are not allowing enough time for the free wheeling shaft to spin fast enough before engaging because the couplers are moving too fast from the short shifter. So, not much time is spent on the friction stage of the synchros.
It's a good idea to "feel" the car when adding mods like these. You can shift without clutching if you can rev match between gears (in neutral). If you allow time between gears, but are paying attention to engine speeds, you will almost have no problems with a short shifter.
Having said that, I don't like short shifters but I can shift pretty fast. Although I don't think I can beat the DSG
My 2 cents. YMMV
The only reason for not being able to shift is because the speed of the engaging gears connected to the engine is not synchronous to the speed of the shafts eventually spun by the driveshaft (of a moving car).
When the clutch is depressed, the input shaft of the transmission is allowed to free wheel. This allows the gears connected to the input shaft to freely engage to the spinning shafts of a moving car.
The engaging is done by "couplers" with teeth (not gears) to match teeth with the spinning gears. These couplers contain "synchros". The synchros as dieselgeek describe, allow this smooth transition by having the couplers applying friction to the gears connected to the free wheeling input shaft, have them match speed and then eventually hard engage with their teeth.
The grinding noise is because the shafts are not at matching speeds yet and the clutch is released too soon so the engine speed started driving the input shaft, which may not be in synchronous relationship with the output shaft. It's the teeth of the couplers that grind and eventually wear out, then shifting becomes a pain.
So, add the equation of a short shifter, wherein with the same arm speed, the coupler engagement is faster and sooner. If you are slow with your left foot, then you might not be fully depressing the clutch as you move to engage the next gear. This will eventually cause grinding and damaging of the couplers teeth.
The other thing is you are not allowing enough time for the free wheeling shaft to spin fast enough before engaging because the couplers are moving too fast from the short shifter. So, not much time is spent on the friction stage of the synchros.
It's a good idea to "feel" the car when adding mods like these. You can shift without clutching if you can rev match between gears (in neutral). If you allow time between gears, but are paying attention to engine speeds, you will almost have no problems with a short shifter.
Having said that, I don't like short shifters but I can shift pretty fast. Although I don't think I can beat the DSG
My 2 cents. YMMV
10-21-2005, 08:29 PM
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You can also mess around with different tranny fluid combinations.
Different fluid viscosities and combinations grab the synchros differently. I just switched from a NEO/BG2 mix to a Pennzoil/Redline Heavy Shockproof mix. DSM trannies are a PITA.
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