Mike, this is probably the best post on drive shaft material and is the one I recalled and was hoping to find:
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By Dennis Frisk (Dfrisk) on Tuesday, July 24, 2012 - 08:50 am:
Jonathan S. - NO WAY would I make a CC driveshaft out of SS. For one thing it'd be really expensive, another thing is you can't buy decent SS except at specialty steel outlets for inflated prices. And SS is prone to galling. Any place SS rubs against another metal it tears it up.
The proper 4140 alloy steel is 4140 pre-hardened. Normally it's hardened to around 30 Rockwell on the C scale, about the limit of machinability with normal common tools. If you get 4140 annealed, it's not much better than plain old 1018 cold rolled which was what IH used.
Another great driveshaft material is Stress-Proof steel, which is a registered trade mark of LaSalle Steel, which is 1144 severely cold drawn steel. Machines very nice, every company that makes cold drawn steel makes a stress-proof equivalent. You compare the mechanical & physical properties of 4140 pre-hard & Stress-Proof and they almost identical.
I would not get too far away from stock on the clutch on your 100. With OEM components in good shape your clutch can transmit more HP/Torque than you have traction to use.
I put an aftermarket clutch in my #72 when I installed a hot-rodded K321 several years ago. 4140 hardened drive shaft, billet clutch plates, red spring, extended clutch release lever. It was a PITA to run. Finally after 150 hours the throw-out bearing destroyed itself from constant running under way too much pressure and I went back to OEM parts. I had the old clutch slip a few times before I installed the K321 when I was running a K241, plowing in 2nd gear about 8-9 inches deep. Took excellent traction & lots of added weight to get traction too. And that was using 35 yr old clutch plates & pressure spring.
With the new billet plates, OEM spring I have NO clutch slippage with a strong 14 HP engine.
Don't over-think this clutch. The stock parts work really good and every time you shift you'll appreciate it.<!-/quote-!><hr size=0></blockquote>