pins & needles

[kmcconaughey]

Although I like the full explanation of his build and the sourcing of the parts, I would combine the idea with the build in the post that John G. linked to in order to eliminate the rag joint style flex couplings altogether. I don't know how much movement the square sliding coupling has and would prefer a splined type of coupling to reduce vibration as the tolerances are tighter.
I'm sure a smaller version of one like those found on driveshafts of a car or truck can be found. I thought I noticed ones that might work for this app used on the steering shafts of some cars and trucks. A trip to the junkyard and a little machining and it's a build.

One thing to keep in mind is that the driveshaft in a Cub Cadet spins at around 3600 RPM, which is quite a bit faster than a steering shaft. Make sure that whatever u-joint you use is capable of that.

 

[mgonitzke]

One thing to keep in mind is that the driveshaft in a Cub Cadet spins at around 3600 RPM, which is quite a bit faster than a steering shaft. Make sure that whatever u-joint you use is capable of that.

Yep! Which also means it needs to be well-balanced and have near zero runout. These are not requirements for a steering shaft...

This problem has already been solved...there is no need to reinvent the wheel. 'Cyclops' CV joint driveshaft or 2000/3000 series is much easier to adapt and will be reliable.