> I currently have a non-overdrive all synchro gearbox on my
> TR4, but was just able to purchase a type A overdrive on Ebay
> from Australia. I know that I will need a different
> mainshaft, but if I were planning on taking this in to a
> local shop for conversion, what parts should I try to secure
> before the work can begin.
You'll need the adapter plate for the back of the gearbox. Since the box
has to come apart to install the mainshaft, now would be a good time for new
synchro rings; gaskets and seals. I'd probably do at least the countershaft
thrust washers as well, possibly more depending on how tired the box is.
The top cover also has to come apart to install the (2) isolator switches,
so if there is any sign of leakage from the shifter shaft seals, now is the
time to replace them as well. (Note that the currently available seals
don't always fit and may need packing washers to seal. Just mention this in
the instructions to your shop, they should know what to do.) The isolator
switches are a non-standard metric thread, so you might need to find a tap
for them.
I would also plan to install the cross-bolt, to reinforce the taper pin in
the clutch shaft. Good time to change the bushings the clutch shaft rides
in, too.
Then there's the question of how many bits are missing from the OD itself,
and whether they are in good shape. Make sure you've got the pump cam and
the clutch springs, and the clutch springs aren't "tired". Double-check
that you've got the right speedo drive gears, and the correct rear flange.
I'd want to check the operating pressure before installing it, too.
Randall
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