For the race car, you can keep it in the Triumph family by using a TR6 gearbox.
I have had this in my race car for five years now with no racing-induced
failures. I have the close ratio gearset available from distributors of Moss
Europe, which is really much superior to stock. Make sure you or your
assembler properly clearances the bushings however - I had a spectacular third
gear failure before the cause was determined when the gear seized on the shaft.
The TR6 box is probably a 25 lb weight penalty, and you need to invert the
clutch throwout bearing fork, make a bracket to support the slave cylinder in a
new location, weld in a simple bracket to support the stock TR6 transmission
rear mount, and modify the driveshaft, and a few other minor things.
Good news is, the gearboxes are widely available for very cheap, the close
ratio gears cost less than $1,000, a TR6 engine plate bolts right up to the GT6
engine or you can drill one more bolt hole in the GT6 plate to accept the TR6
box, and the shift lever is in exactly the same location.
Read your club?s rules - SVRA allows this, or did, some clubs say you need the
same number of forward gears, so you have the overdrive exemption that allows a
five speed, but some clubs, for example VRG, require that your gearbox have the
same external casting as stock, but internals are free.
I happily traded vintage purity for reliability and a weight penalty, since I
was replacing gearboxes every other race weekend. Now the weak link in the
driveline is the diff, which seems to fail every three years or so.
On Feb 21, 2018, at 11:46 AM, Vince G via Fot <fot at autox.team.net> wrote:
Seeing the recent discussion on Type A Overdrive I thought I?d take advantage
of this great knowledge resource and ask opinions on restoring my street GT6 OD
that failed last year (worn out basically) versus abandoning the triumph set up
for a T9 retrofit while still available.
What is anyone?s experience with regard to longevity of a Type A overdrive.
This is my simplest, lower cost solution (about $800) versus the T9 swap at
about $4000
Additionally I need to get my Track Car also a GT6 up to snuff. I understand
there may be an option of having someone restore and upgrade the current
triumph 4 speed versus me purchasing the T9. In this case reliability and
operability are more important to me than keeping the car period correct. I
can?t afford the time or money to repeatedly swap out a weak transmission
that?s prone to failure like a stock box.
Advice and Opinions most welcome.
Thanks everyone
Vince (from Ontario Canada)
69 GT6+ #144
VARAC
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