[Healeys] BJ8 gearbox rebuild

A H List austinhealeyslist at gmail.com
Thu Jun 8 01:23:57 MDT 2017

Hi Guys,

Looking for somebody that has experience with the BJ8 gearbox,
particularly the extra radial pins inside the synchroniser assembly.

The two pins inside the 3-4 hub and one in the 1-2 hub appear to be
added to stop the hubs vibrating backwards and pressing on the
opposite baulk ring when a gear is engaged since there is nothing to
prevent this on the earlier boxes. What confuses me is that they don't
actually do that in the BJ8 box because the grooves machined into the
mainshaft are too wide and allow the hub to move all the way over and
touch the opposing baulk ring anyway.

The reason I ask is that I'm part way through assembling a hybrid BJ8
gearbox with a straight cut gear set that uses some features of the
earlier box and some of the later type. It has individual needle
rollers in the first motion shaft instead of the caged bearing but
also has the larger lay shaft and caged bearings. The issue is that we
have to use an earlier mainshaft to match the first motion shaft
internal needle bearings but then the pins mentioned above don't have
the necessary grooves to engage into.

Pics attached are of one of the pins in question, and the grooves
machined into the BJ8 mainshaft. It appears that the pin is pressed
inwards by a ramp machined into the engagement collar as the gear is
engaged and it goes down into the groove on the mainshaft- which in
theory locks the hub from wandering back to the opposite side.

Questions: Should I ignore the pins as unnecessary? Should I machine
the mainshaft to allow the pins to operate as (I believe) they should
work? Should I machine the mainshaft so the pins work as they did in
the BJ8 box, i.e. not at all?

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