[Fot] OD rebuild or T9 Trans. GT6

[gt6steve at aol.com]

I'd like to reinforce Scott's excellent observations.  His is exactly what I would've said if eloquent.




-----Original Message-----
From: Scott Janzen via Fot <fot at autox.team.net>
To: Vince G <vangoughv at hotmail.com>
Cc: 'Friends of Triumph' Triumph <fot at autox.team.net>
Sent: Wed, Feb 21, 2018 3:36 pm
Subject: Re: [Fot] OD rebuild or T9 Trans.  GT6


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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