In a message dated 4/16/02 10:40:12 PM Pacific Daylight Time,
owner-mgs-digest@autox.team.net writes:
> An overdrive gearbox uses a shorter mainshaft, after which the overdrive
> unit generally bolts up to the back of the main housing in place of the
> original tail housing. Overdrive mainshafts for the MGA gearbox may well
> be non-existent, as the car was never built that way. This problem even
> applies to the MGB which did have a couple of different overdrives
> available, but the mainshafts for those overdrive gearboxes are currently
> not available as spare parts, so you generally have to buy a complete
> overdrive gearbox just to get the mainshaft.
>
Barney - you are correct, there were no mainshafts from MGAs to suit the
Laycock OD unit. You are also correct in saying that the easiest way to do
the conversion is to buy a used 1963-1968 MGB OD trans. You can then use the
mainshaft from the B box in the A, and bolt the OD to the A front casing.
While you are at it, if you end up with a late (68) box, have the A main case
reamed to suit the larger 4 bearing laygear and shaft used in those
transmissions - no big deal to do, and a much better set up.
> So this problem gets down to how much cutting and welding and other
> modification you are willing to do to fit a non-standard overdrive gearbox
> into the MGA. The biggest problem with the overdrive units is that they
> are rather wide aft of the main housing, which generally requires widening
> the tunnel to make them fit. The early MGB 3-syncro unit is a bit smaller
> (narrower) than the later 4-syncro unit, and would be easier to squeeze in
> with less radical modification of the tunnel. But the earlier MGB unit is
> also more rare, and either one requires some cutting and welding to
> fabricate a new rear mount for the gearbox.
>
I would not use the late all synch box for the reason stated - bigger and
harder to make fit (and I don't like the box as well as the early non-synch,
but that's just me).
You have a couple of issues in fitting the OD box in an A. The shifter from
the B gets used, and it comes out further forward than the stock A, so you
have to modify the top of the trans tunnel to look right, and unless you also
modify the shift lever, you'll be barking your knuckles on the underside of
the defroster control panel all the time.
Second, is mounting the trans on the frame. Unlike many, I don't believe in
cutting the stock ears off the A frame. I make up a bracket that mounts the B
tailshaft/OD housing to the stock A mount, but bear in mind that this
eliminates the rubber mount, if you want to have driveshaft U joint angles
within spec, and you might get some additional vibration into the passenger
compartment.
Third, the OD unit is widest right where you don't need it - by the handbrake
level and mechanism. You'll have to bulge the tunnel anyway, but you need to
get creative to also keep the handbrake functional.
>
> Now if you don't mind some non-MG parts in your car, and you have about
> $1400 burning a hole in your pocket, you can buy a 5-speed gearbox setup
> that is (for the most part) a bolt in conversion for the MGA.
True. I prefer using factory parts, but then we already know I am a
reactionary!
>
> Or if you want to get a little more whacky you can do a different 5-speed
> gearbox and slip in a 160hp fuel injected V6 engine along with it. I still
> don't personally recommend this, but for kicks you can check here:
>
The GM V6 kits are interesting, but while I don't particularly care about a
few more ravaged MGBs, I'd hate to see anyone chop up an MGA that way. It
does make me wonder how my street Fiero engine (non-stock - I built it and it
is a 3.2 turbo with around 300 bhp) would work in an MGA - might be very
expensive on tires........
Bill
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