70 thansaxle mainshaft

[jjemg]

I have heard talk about changing 901 914 mainshafts for v8 conversions. What I am tackling is changing 901 911 gearbox with sideshift 914 901 so to use 225mm clutch for 3.0 engine in my 914/6.I may use this car for solo 1 or 2 and will change the plate during rebuild but am concerned about shaft. hoping for somebody that knows for advice.
Thanks
jimmy

[Grady Clay]

Jimmy,

There are several BIG issues here.

Yes, the 901 input shaft in 1st gear is a potential weak point. That was particularly true for the ’64-’67 901s that had a smaller diameter threads/nut at the fixed first gear. Even a 2.0 should replace that part.

I have 901/911/914 in two competition cars; a 2.0-2.5 ‘68 911 and a 2576 (91x66) SCCA GT2 914-6. They work great, but are in low torque – high rpm application (the 2676 HP peak is at 7800 and still pulls to 8800.) The 215 mm C6 flywheel and ‘69S Alu clutch is not receptive to standing starts.

For auto-X I recommend a 915. A 3.0 with a 901 and you trying to smoke it off the line is an invitation to disaster.

If you are determined to keep a 901/911/914/904/906/910 transmission, then make it a 4-speed. That puts the 1st gear on the main-shaft. There are ratio choices from “A” thru “GA” and more. You also want a clutch that you can slip under power. That necessitates a 225 mm clutch, a tolerant disc, and your willingness to change it periodically.

Best,
Grady