Most 150S cars have/had the CR gearbox and obviously some regular 150s did
too. Doc is right about the designed use of the CR box for racing purposes.
But it isn’t needed for street driving. [My MGA Twin Cam with CR gears can
be a pain on the street, and I live on the Prairies without hills!!!] The
CR suffix on your gearbox number identifies the gear set inside. A JLS
prefix would indicate the presence of OD.
Overdrive is nice (again, I’m on the Prairies) but if you don’t have it
presently, then perhaps the 5-speed option later on would be good for a
‘driver’. Going through the expense of converting to OD, just for the OD,
wouldn’t be worth it (IMHO) as you would still have the non-synchro 1st
gear. With the 150, overdrive isn’t essential for highway use (unlike with
most MGs and TRs and even A-Hs), as the relatively high axle gears that came
with the non-OD cars and the 16" wheels make for relatively low revs at
(150S with OD gearbox JLS40444CR)----------------------------
From David Massy:
So how unusual is CR? Is it something that whilst not standard was thrown
into alot of Jags as they progressed down the production line, is it just a
little unusual, or is it unique? Having never had the pleasure of driving my
car I have no experience of a CR. Can anyone comment on how much of a
difference it makes?
On a slightly separate not, I’m told that OverDrive makes a huge difference
on long distance cruising, but I’m unsure what to do about it. Is it
feasable to add it to the existing transmission? I figure that maybe that
isn’t a good idea because as I understand it the O/D eqipped cars had
different ratio gears. My current intention is to leave it be without OD and
if it proves to be an issue for me later then I’ll swap it out for a modern
toyota or vicarage 5 speed to bring the whole thing uptodate and mothball
the old gear box.
Gearbox number:- JL42104CR<