Re: Alfa33 1st gear synchromesh problems

[Simon Favre <favres@engmail.ulinear.com>]

A few additional comments on the 1st gear crunch issue.  The 1st gear
synchro works when downshifting to 1st while the car is moving, not when
it is still, as described.  With only one of those little "shoes" inside
the synchro ring, it will expand when the friction rotates it one way,
and it will not expand when rotated the other way.  Which way the ring
gets turned depends on which shaft is spinning faster.  At a stop, it's
a sure bet the input shaft is going faster.  When moving, the output
shaft is usually going faster on a downshift.  That's why blipping the
throttle helps.  It makes the two sets of engagement teeth (one on the
gearwheel, one on the sliding sleeve) move at the same rate (when done
properly), thus putting minimal wear on the synchro ring.

Note that when the car is idling at a stop, ALL the rotating parts in
the gearbox are moving EXCEPT the output shaft, synchro hubs and sliding
sleeves (and the reverse idler).  The input shaft turns with the motor.
The input shaft drives the countershaft, which in turn drives ALL the
gearwheels.  When you step on the clutch and grab for 1st, you are
trying to stop all that rotating mass with the engagement teeth.  Ouch.
Please get into a habit of shifting into 4th at a stop before trying to
engage either 1st or reverse.  Why 4th?  Because it doesn't take nearly
as much abuse as 2nd, that's why!  Reverse is a straight-cut gear with
no synchro.  It will always crunch unless you either wait for the box to
stop spinning, or touch 4th first.

It is true that if your clutch is dragging on the flywheel, for whatever
reason, you will not be able to engage any gear without some effort and
some noise.  The most common cause of this is hydraulics, but a damaged
pressure plate or friction disk can do it too.

>It appears to me that no one really understands the Alfa 33 or Alfasud
>or 105 or 116 gearbox first gear synchromesh.  Synchromesh when
>selecting first gear from neutral on all Alfa models mentioned, up until
>the Alfa 90 and / or GTV6 with the "Isostatic" change mechanism was very
>bad.  The reason for this is that there is no synchromesh when effecting
>this change, due to the omission of the "brake shoe" on the inside of
>the synchronizer of first gear.