Diff aside, the basic box is the same as the full synchro MkIV Spit. The
differences are that all the gear ratios changed and the input shaft is
longer and beefier for the GT6. The cases and main shafts as well as a few
other bits are interchangeable but have different gears and input shafts.
If the gears are beefier, I haven't seen anything that says so but it
certainly makes sense.
But since the basic boxes share a common design, they suffer from the same
problems.
Putting a Spit box into a GT6 is quite impossible since the input shaft is
fat too short to span the depth of the GT6's bell housing. And it would be
folly to try and use the spit bell housing because the Spit clutch would be
way inadequate to handle the torque of the 6.
Joe
-----Original Message-----
From: triumphs-bounces@autox.team.net
[mailto:triumphs-bounces@autox.team.net] On Behalf Of jimmuller@rcn.com
Sent: Wednesday, October 15, 2008 10:16 AM
To: Triumphs@autox.team.net
Subject: Re: [TR] GT6 Transmission
Joe "Fluif" Curry wrote:
> Comparing with the MkIV gearbox which uses the full synchro
> 3-rail, it is basically the same box that was used in the
> GT6 but with different gear ratios. The GT6 has a closer
> ratio selection of gears than the Spit box.
It was my understanding too that they beefed/hardened up the gearing and
diff for the GT6's higher torque. I mention this only because the question
smelled like someone hoping to drop a Spitfire gearbox into a GT6. Others
may disagree but it doesn't sound like a good idea to me. The GT6 gearing
is unique and part of its charm. 3rd and 4th are close together, redline in
2nd is 65mph, redline in 3rd is 96mph, etc. Not that I ever quite push mine
to redline but the available speed headroom in but 2nd and 3rd are (ahem)
useful.
> Also, the input shaft is much larger in diameter and
> longer than the one used in a Spitfire.
As a practical matter, this means that a Spitfire clutch alignment tool
won't work with a GT6 clutch!
--
Jim Muller
'80 Spitfire
'70 GT6
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