it seems most of you are talking about A type stuff, none of this is
relevant to the posters query on J type
if anyone wants a really tuff A type, then look for the ones made by
Italians A.E. Bianci under licence to Laycock, for Ferrari (330 models etc
up to 1965 when the 5 speed came into use). These use the "conventional"
Laycock front case but have a much bigger rear case with huge planet gears
and pins, to better handle the torque of the big ferrari
for the J type. we use modified Dolomite Sprint & Volvo ones as they have a
fuller front case making it less likely to distort. I still have the
laycock drawing re mods to the pistons in the early versions of these
o/d's, but as these have not been around for years , it is probably
irrelevant.
best to start with a unit from early 80's Volvo 244 or go buy a brand new
one from Gear Vendors in USA
the changes needed to the J type for race use are:
- open up the Z port drilling
- shim up annulus gear to reduce clutch travel to its absolute minimum
- check the lining & carrier is true and not wobbling (this causes
erratic contact patches)
- fit new nitrided planet gear pins & cryo treat the gears & needle
bearings
- very careful assembly of the hydraulic valve in the solenoid
we get about 3-4 years racing per rebuild. we have no noticeable slippage
on change and can make a change into overdrive faster that a change of
gears. by using a carefully selected ratio set, we can get a very useable
3rd overdrive which we race with all the time in our Historic 2.5PI
Terry O' Beirne
Australia
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