> Chuck---I too am considering the 5 speed box by Toyota. If I
> had a TR6 OD unit I would probably stay with the original setup.
> But I don't, and high mileage on my tranny will make something
> happen here eventually. The gear spacing options will give me
> what I need, with a .85 final drive and a lower 1st ratio. One
> hangup is no speedo connection, and a price of U.S. $2000.
> Or is that two hangups?
Dick, Chuck, and everyone else interested.
I used to think the Supra 5 speed was the way to go, for a gearbox for the
TR6. That is until I found out about a company which uprates overdrives
here in the USA. Why settle for 5 gears, when the uprated OD is strong
enough to be used in competition in all 4 forward gears (8 total ratios).
Price isn't bad either, it's $1200 for a fully rebuilt and uprated OD
unit... you must provide the core for rebuilding. This is avaliable from
Medina Motorsports in Ohio, 330-725-2725. Essentially what they do is (a)
replace the friction material in the OD with something which is much more
durable and can transfer quite a bit more torque (b) replace some of the
spinning bearings and likewise with ones again that can cope with the
greater transfer of power and finally (c) increase the hydraulic pressure of
the overdrive unit for instantaneous engagement.
The overdrive provides a more useful top ratio, and keeping your hands on
the wheel during competition (esp. autocross) is quite an asset, as all it
takes to switch up to next ratio is a flick of your finger. Acceleration
can be vastly improved also, with the ability to use OD in the lower gears
as extra, intermediate gear ratios.
Then we also have the argument for purity, an overdrive quite simply wins
out here over the Toyota Supra gearbox. Hell might as well just throw in
the Supra motor as well ;-) Triota has a nice ring to it! heh
And Dick, in your case, you can probably find an overdrive fairly cheaply if
you look. In June, I purchased a working complete A-type overdrive gearbox
from Missouri for $400... probably one of the best deals I ever got on
anything in my life! It even came with some spare components. I've bench
tested it and all is well, but it will probably be sent off to Medina this
winter so that it will be ready to mate up to the supercharged TR6 motor
which is nearing completion.
If you're worried about the integrity of the rest of the gearbox, well...
they were rallied in numerous 50s and 60s rallies in the TR3 and TR4 all
with overdrive working on every gear, the TR250/6 gearboxes are essential
the same with different ratios, and now even more uprated components are
available such as heavy duty layshafts.
I don't think there is any reason to not stick with the Triumph gearbox and
overdrive, they can cope with power well and they can be made to cope with
even more power for less money than purchasing a Toyota Supra gearbox
conversion.
Kai
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