Specifications

GEARBOX AND DIFFERENTIAL ASSEMBLY
A close ratio 'dog type' gearbox kit has been
specially developed for this model. This gearbox
utilises the casing and intermediate housing or
' sandwich plate' from the standard car's F13
speed gearbox but the component parts of the
close ratio kit must be assembled along with a
revised end cover and gearshift cover assembly.
As this is a heavy-duty gearbox unit, many of
the component parts are larger that the corre-
sponding standard item. To accommodate these
some detailed internal modifications must be
carried out on the casing BEFORE commencing
assembly operations.
CASING MODIFICATIONS
The following operations are required within the
area normally containing the DIFFERENTIAL
UNIT.
Remove the speedometer drive gear assembly
and blank off the hole with the blanking plug
supplied. The speedometer drive gear support
l ug can now be removed by grinding away
the excess material. Also 'chamfer' the region
adjacent to this blanking plug and remove
excess material by creating a 'flattened' profile
to the area immediately above the centreline
of the differential bearing housings. This will
give the additional clearance required for easy
i
nstallation of the differential assembly. Clean
off all internal rough edges due to variances in
castings to give clearance for the crown wheel.
The following operations are required within
the area normally containing the GEARBOX
ASSEMBLIES.
The reverse gear shaft support housing is
already machined to 'convex' profile, this must
be further modified by grinding to a 'rounded'
profile. To ensure COMPLETE engagement of
the dog teeth in 4th gear, the 1st/2nd
and
3rd/4th gear selector shaft support housing must
be spot-faced, removing 1.5mm from the entire
face of the casting at this point. The casting must
also be relieved by further radiuses in the corner
of this area, to give additional clearance between
the casing and the selector fork enabling it to butt
against this machined face. The amount to be
removed can easily be determined by inserting
the selector fork and shaft into position in the
casing as a guide. Since the 4th gear wheel is larger
than the standard item, a considerable amount
of material must be removed from the casing at
the point where the gear cluster encroaches into
the differential housing. Approximately 2mm
clearance is called for when assembled, and this
clearance can be viewed through the aperture in
differential case when the gearbox cluster is fitted
i nto the casing.
Modifications to INTERMEDIATE HOUS-
I NG or SANDWICH PLATE.
The mainshaft bearing housing will foul on
the 1st gear wheel unless the casting marks
are removed by rounding off the affected area
before assembly. The amount of material to be
removed can easily be confirmed by offering up
the mainshaft complete with the gear. All the
above mentioned points are highlighted in the
illustrations for this chapter.
GEARBOX ASSEMBLY PROCEDURE
It is very important that all the parts required
are thoroughly cleaned prior to commencing
reassembly of the gearbox and a clean, swarf-free
area is reserved for the build.
Carefully remove all gears from the mainshaft,
since they have only been fitted loosely to the shaft
for packaging purposes. It may be prudent to note
the sequence of this assembly and confirm with
the diagrams provided.
The final drivegear pinion is integral with
the mainshaft, but prior to further assembly
carefully
fit the spacing washer behind the
gear, making sure that the small locating ball
i
s correctly located in the small hole provided in
the shaft and spacer, thus preventing the spacer
from revolving.
Now lightly lubricate the roller bearings and
slide over the mainshaft, along with the gear
wheels and selector hubs in the order and
position shown by the exploded diagrams and
photographs.
NOTE: If the donor gearbox has already cov-
ered a significant distance, renew the mainshaft