Prelude Synchros
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A Philanthropical Fruit
Joined: Sep 2004
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From: Ann Arbor Michigan Aim: nickbeier
Prelude Synchros
I posted this in the engine tech forum, but they don't talk much there 
Alright, so on most cars there is a lock on first gear, so you cannot (accidentally or intentionally) downshift into first gear at a speed to high for the engine at that given ratio. The lock, as I'll call it, continues on my car down till almost 4mph, I almost need to come to a dead stop untill it lets me easily shift into 1st. I don't think this is an actual locking mechanism however, it's simply the synchros on the gear box don't synchronize the transmission untill your car slows to that speed.
But the other day I was told that if I blipped the throttle rather high (sort of like in heel toe) it would let me into first gear at higher speed - and it worked! I use this method often now, but I truley don't understand it. If the clutch is in this whole time, how can revving the engine effect the synchros? I thought the clutch disconnected the engine from the tranny, so they could operate independantly. Thanks guru's.
Alright, so on most cars there is a lock on first gear, so you cannot (accidentally or intentionally) downshift into first gear at a speed to high for the engine at that given ratio. The lock, as I'll call it, continues on my car down till almost 4mph, I almost need to come to a dead stop untill it lets me easily shift into 1st. I don't think this is an actual locking mechanism however, it's simply the synchros on the gear box don't synchronize the transmission untill your car slows to that speed.
But the other day I was told that if I blipped the throttle rather high (sort of like in heel toe) it would let me into first gear at higher speed - and it worked! I use this method often now, but I truley don't understand it. If the clutch is in this whole time, how can revving the engine effect the synchros? I thought the clutch disconnected the engine from the tranny, so they could operate independantly. Thanks guru's.
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Joined: May 2003
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From: Long Island, NY
u are right about the clutch idea except the mainshaft is touching the flywheel where the pilot bearing goes, theres no pilot bearing on H+F series flywheels but both surfaces are machined. so no the mainshaft still maintains "some negligeable" rotation from the flywheel. i always found i had to let the clutch in, rev it and then clutch it again before getting into first.
this seems to affect preludes only from what ive heard. as far as why, dont ask why because it affects 99%+ of 1992+ preludes, so its either a 10 year design flaw or an engineered outcome. I put my money on the latter.
Having taken my tranny apart several times now (last time was late NOV), i dont see any obvious internal reason why.
If i had to guess tho, i would say it has something to do with the design of the 5th/R shift fork and how that plays with the first gear and the reverse idler gear, because reverse is 1st gear synchro hub+reverse idler gear. The reverse shift "fork" if u can call it that is this odd L shaped thing that forces the reverse idler gear into place. At the same time the 5th/R synchro sleeve locks to the end of the mainshaft on this "fake" synchro ring.
Which causes the counter shaft to spin backwards since there is an extra gear between the main and counter shafts now. The reverse idler hear engaging is also responsible for that loud clunk whenever you throw it into reverse.
~kris
this seems to affect preludes only from what ive heard. as far as why, dont ask why because it affects 99%+ of 1992+ preludes, so its either a 10 year design flaw or an engineered outcome. I put my money on the latter.
Having taken my tranny apart several times now (last time was late NOV), i dont see any obvious internal reason why.
If i had to guess tho, i would say it has something to do with the design of the 5th/R shift fork and how that plays with the first gear and the reverse idler gear, because reverse is 1st gear synchro hub+reverse idler gear. The reverse shift "fork" if u can call it that is this odd L shaped thing that forces the reverse idler gear into place. At the same time the 5th/R synchro sleeve locks to the end of the mainshaft on this "fake" synchro ring.
Which causes the counter shaft to spin backwards since there is an extra gear between the main and counter shafts now. The reverse idler hear engaging is also responsible for that loud clunk whenever you throw it into reverse.
~kris