[Fot] GT6-Spitfire Transmission Conversion

[Anthony Parker]

The published ratios are obviously a combination of two real ratios, so it's theoretically possible.

When I was investigating this swap years ago, I seem to remember one hurtle was a miss match between the pilot diameter on the main shaft and the bore in the input shaft. Several different caged needle bearing options as well. Can't remember if I found a combination. Other things took over.

Begs the question, were there ever two transmissions made with the same parts? 😁




Anthony Parker, Mechanical Engineer
________________________________
From: Fot <fot-bounces at autox.team.net> on behalf of JOE CURRY via Fot <fot at autox.team.net>
Sent: Thursday, October 12, 2023 12:37 PM
To: Barr, Scott; Barr, Scott via Fot; Rod Pierce
Subject: Re: [Fot] GT6-Spitfire Transmission Conversion

Since the GT6 gearbox has a different gearset than the Spitfire has, I can't see how that would work.  The first gear for the 3-rail Spitfire has a ratio of 3.75 compared to 2.65 for the GT6, therefore the input shaft gear won't mesh with the gears in the GT6 box.  Here is a link to the summary of what I did way back in 2000 when I adapted a Mk3 GT6 gearbox to work with a small journal 1296 that I used in my autocross prepared Mk1 Spit:  https://www.geocities.ws/MotorCity/Speedway/1080/gt6boxtospit.html.

Joe
On 10/12/2023 9:31 AM EDT Barr, Scott via Fot <fot at autox.team.net> wrote:


When I had this done some years ago, I took the job to a local racer-transmission guy.  After fiddling with it a bit, he just put the Spitfire input shaft into the GT6 trans and it worked fine.  GT6 gearbox for my Spit racer, no cutting, welding, etc. required.  It worked great for a few seasons until I pulled it to install an overdrive trans.

Could just be luck?  I understand that there are a number of variations of gear constructions and maybe I just happened to bring him two that matched?  Who knows.  But it worked for me.

Scott (B.)

From: Fot <fot-bounces at autox.team.net> On Behalf Of Rod Pierce via Fot
Sent: Thursday, October 12, 2023 7:57 AM
To: Rod Pierce via Fot <fot at autox.team.net>
Subject: [Fot] GT6-Spitfire Transmission Conversion

I have a GT6 transmission in my spares collection and I have heard they can be converted to run in a Spitfire.

I'm interested in accomplishing this over the winter and I am looking for information/advice on the best way to do it.

It is my understanding that you can have the GT6 input shaft either machined to fit or you can cut the input shafts from a GT6 and a Spitfire and weld the Spitfire on the GT6 transmission.

Thanks


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