In a message dated 98-04-20 22:05:20 EDT, you write:
<<
I don't know if you have put this topic to rest or not but I
thought I might shed some light on it. I have a '58 MGA with a 4.55
rear
end in it. As you probably already know the A's came stock with 4.3
gears except for Mk IIs which had 4.1 rear ends. I run the 4.55
on the street all the time and though it is a bit busy it is still
quite acceptable even at 65-70 mph cruising on the freeway. I have
the
stock wide ratio gears but I also drove a Twin Cam with a close ratio
gearbox and 4.55 rear end and it too was streetable. In fact the
4.55 rear end is better suited to the higher first gear of the close
ratio gearbox. I havn't tried the 4.55 gears for vintage racing as I
retired the MGA from racing some years ago but they work well for
autocross. The biggest problem I had with the 4.55 was finding a
set. When I got mine some 8-9 years ago they were quite scarce. At
that time I was trying to put together rear ends of all available
ratios,
3.7- MGC unlikely to fit without special work
3.9- MGB readily available
4.1- MGA MkII, dificult to find
4.3- MGA all but MkII, readily available
4.55- MGA, optional and rare
4.875 Racing option for MGA, may be the same as late T series ring
and pinion
5.125 Racing option for MGA, may be the same as late T series ring
and pinion
These last to would have limited use but would round out the choices
that were available to MGA owners. A couple of other thoughts
to consider are the effect of different tire diameters between MGA's
and B's and the fact that your speedo will be affected with each gear
change. For the MGAs there
were different speedos for each different gearset, for the B's I
think they just changed the angle gear drive ratio at the
transmission for
each different ratio rear end.
Anyway, enough rambling, If you can get a 4.55 go for it and throw it
in, you will be happy on the street and track. Who looks at a
spedo anyway?
Robin
PS, As far as 3 synchro vs 4 synchro boxes are concernd if I
remember correctly you can only swap one direction, I don't remember
which it is though. ie- early box will fit late engine, late box
won't fit early engine or it may be the other way around. The
problem is
the diameter of the pilot bearing and input shaft. Don't quote me on
this part.
Robin,
You have lots of experience with the MGA. And you're right lower is better.
Remember in vintage racing, the tire size is much smaller on the MGB so that
the ratio can be somewhat taller than on a MGA. I have a 4.10 in my MGA road
car and like it for long distance driving better than the 4.30s with the
165x15 radial tires. My MGB vintage racer is very busy with 4.30/1 gears and
185/60x14 racing tires. The 4.30 with these tires are also great for
autocrossing. I also have close ratio gears and turn about 90 mph at 6000
RPMs in 4th.
The early gearbox with the skinny input shaft will fit early or late engines
by changing the pilot bushing, the late gearbox with the large input shaft
will only fit late engines.
Cheers
Rod Schweiger
'64 MGB Sebring Replica #119
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