I have been fixing these units since new.
The A & J are not really comparable and its not reasonable to make
detailed technical comparisons. However, the A has an active accumulator
which stores hydraulic pressure ready for use. The J does not, but
replies on a high pressure pump to work on demand. Both use an identical
sprag clutch to transmit the drive and allow over-run.
The maximum torque values quoted by laycock are quite different, with
the J type being superior. A modified J type, called the P type is still
made and used as an aftermarket accessory on SUV's including the V8
diesel.
The best "racing" modification with both version is to reduce end floats
so the cone clutch works with minimal travel. ON the J type this
requires the typically damaged alloy clutch centre to be modified. If
anyone wants more detailed info on modifying units, please email me
direct.
I use a much modified J type in all 3 of my Triumph race cars.
Terry O'Beirne
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