[TR] OD lubrication

[Randall]

> There were also two 
> A-types, the later one redesigned for softer engagement, so 
> that may be a consideration in selecting oil weight.

FWIW, these actually overlapped.  The "softer engagement" models were fitted
to cars with IRS; apparently because the IRS couldn't deal with the "kick in
the pants" delivered by the earlier units when shifting under throttle.
But, solid axle TR4As still got the harder shifting version.

Randall