Here is some info from Pete Snidal:
Replacing the Detent Plunger
In order to replace the GOSA, the shifter quadrant must first be
relocated to the smooth spot between two gears, as detailed
<file:///D:/DLX2013/9detent.htm#posn>above. (ie, between top and 3rd)
so that the chisel tip won't be caught in a notch and prevented from
turning, since it must turn with the threaded barrel. Engage the
threads of the GOSA, and screw it down until it stops. Once the
barrel has been threaded in to the desired (you think) tension
position, moving the bellcrank by operation of the shifter mechanism
will allow the tip to engage a slot.
It is of course important that the chisel tip be positioned
horizontally, so that it will engage properly with the notches, once
the job is finished. Make a note of the angle of the screw adjuster
when the plunger nose is horizontal, and ensure that when you replace
and adjust, that the screw slot stays in this relationship. Usually,
the chisel is parallel to the screw slot. When satisfactory action
has been attained, holding the screw with a suitable screw driver,
tighten the locknut.
Once you have worked the gearbox through the gears a few times, and
are feeling positive "stops" between them as the detent plunger
engages the appropriate notch in the shifter bellcrank, reassemble
and road-test. This procedure will correct the vast percentage of
shifting problems. If shifting difficulty is still experienced with
the detent plunger working properly, the problem can only be the
linkage moving too far, or not far enough. For example, if difficulty
is experienced getting into top gear from third, the linkage is not
moving far enough in the upshift direction. If it consistently fails
to get past Neutral from second, the difficulty is lack of sufficient
movement in the downshift direction. Note also that not enough
movement in one direction is often accompanied by too much movement
in the other. For example, if insufficient downshift movement is
experienced (missing first from 2nd), excessive upshift movement may
make for attempts at 3rd from 2nd going past 3rd into the 3-4 "false
neutral." To correct shifting problems once satisfied with the detent
plunger, see the section on <file:///D:/DLX2013/9shftadj.htm>ratchet
adjusting.
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Best of luck with it,