[TR] GT6 Transmission

trdoctor at aol.com trdoctor at aol.com
Wed Oct 15 11:14:39 MDT 2008


Thanks for the information, Joe.? I appreciate it.? The gearbox is noisy in 1-3 and quiet in fourth.? It also can't be rushed into 2nd or it will bark the synchro.? It downshifts just fine which is puzzling.? Usually they are just the opposite.

Sam


-----Original Message-----
From: Joe Curry <spitlist at cox.net>
To: trdoctor at aol.com; triumphs at autox.team.net
Sent: Wed, 15 Oct 2008 10:55 am
Subject: RE: [TR] GT6 Transmission



It all depends on which Spit gearbox you are comparing it to.

The GT6 boxes are 3 rail design which was dropped in the later Spits in
favor of the single rail.

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.
Also, the input shaft is much larger in diameter and longer than the one
used in a Spitfire.

The D Type OD unit was used on all Spit Boxes up until the early 1500 models
when it was replaced by the J type.  The GT6 uses the D type OD throughout
but theoretically you could implant a J type if you can find a 3-rail  full
synchro Spit box with a J-type and use the main shaft and adapter for the J
Type and implant them onto a GT6 box.  However, I would expect the main
difficulty would be in actually finding one of these combinations to start
with.

It should be noted that the GT6 boxes are highly desired by Spitfire racers
because of their gear ratio.  To adapt a GT6 box, the input shaft is cut
down and a different clutch plate is used to fit the 10 spline 1" shaft.

Joe

-----Original Message-----
From: triumphs-bounces at autox.team.net
[mailto:triumphs-bounces at autox.team.net] On Behalf Of trdoctor at aol.com
Sent: Wednesday, October 15, 2008 8:36 AM
To: triumphs at autox.team.net
Subject: [TR] GT6 Transmission

Does anyone know if the Spitfire and GT6 transmissions are the same and use
the same overdrive?

TIA

Sam
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