REGARDING XK120 Moss Gearbox-2
Haven't heard anything from anybody about Moss gearboxes, Moss gears, G.G.Co.,
or any other cars using Moss gearboxes. Is there nobody that knows anything at
all about these?
I did find a reference that Moss gearboxes were used by Aston-Martin and
Triumph in the 1930's.
I now know why the thing was popping out of second gear. I wrote before that on
the internal teeth of the first gear wheel with the rear part of one tooth
relieved, the unrelieved forward part of that tooth was deformed into a furrow
shape by the plunger/ball. That tooth was thus wider than it should be, and it
was too wide to engage properly with the external teeth on the rear of the
second gear wheel, thus preventing the first speed wheel from moving all the
way forward into second gear engaged position. That wide tooth has now been
filed off back to normal width, so it should go into second and not pop out
anymore. I thought these gears were supposed to be harder than a woodpecker's
lips, but apparently not.
As for getting stuck in first, I have decided to machine a relief in the tooth
exactly opposite to the one relieved tooth, thus making the second tooth the
same as the first tooth originally was. Then I can install the first speed
wheel on the second speed synchroniser sleeve 180 degrees from where it was.
These can go on the mainshaft any of six ways, so I will assemble them in one
of five ways so the ball/plunger will not pass over the damaged dimple on the
mainshaft.
The internal cone of the second speed synchro sleeve and the external cone of
the second gear wheel are burned and some metal has been abraded. This is
likely due to the two trying to synchronise together while the thing was stuck
in first gear, which they couldn't do because they were moving at different
speeds. So now I regret having driven home that quarter mile stuck in first.
When it was stuck in first, the second speed sychro sleeve was forward as far
as it would go against the second gear wheel, and the first gear wheel was as
far back as it would go, so that the six spring-loaded balls and the one
ball/plunger were protruding part-way out beyond the forward face of the first
gear wheel. I now see it would have been better if I had tried to prybar the
second speed synchro sleeve back to the rear, instead of beating the first gear
wheel forward. The furrowed tooth and dimpled mainshaft appear to be due to my
hammering. I'm still not sure exactly why it got stuck in first in the first
place. I originally suspected the plunger, but it's not worn. I can't tell if
there is a design defect or just too much wear in the parts. Possibly the
synchro cone is worn enough to allow too much movement.
Last October when I first mentioned this problem on the net, someone else
mentioned a stop pin on the second speed synchro sleeve to prevent this
problem, which my car never had, but was in later XK120's and subsequent
models. I would like to see if I can put such a pin on my sleeve. Anybody know
details of this stop pin?
More later,
Rob
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