Not all billet input shafts are created equal, how the splines are cut on the ends makes a difference. Some shafts have recesses cut into them for tooling, CK's does not. Where the recess is cut seems to be the weak point.

Look closely. Stock





My CK 300m

 

The recesses below the front most splines aren't really the "weak point" per se, but Chris's addition of more spline engagement is a nice touch. He also removes the largely pointless undercuts which are slowly becoming the standard for 300M input shafts lately.

ALWAYS upgrade your input shaft before your main shaft. A stock main shaft can last a long time at very high power levels. They can break though, and at some point they do need to be upgraded, but the input shaft always comes first.

 

Dang, nothing can be easy. Get the billet one, wait, they can be brittle , maybe this one maybe that one. Is the one CK 4340 one they sell now good? Saw where a guy on tech snapped a couple of em years ago. Hard to know what to trust these days.

 

Ill be putting in all those billet CK goodies that Pat has this winter also ,


Slowec , my stock 80E/transgo shift kit has been great , no issues with any hard parts breaking under my weight/power. But my first gear is slipping , so while she's out I'm going to do the CK shafts/ billet hub and dual feed mod . Should be the first and last time I need to mess with it hopefully

 

My Jakes level 2 lasted over a year, but I want to leave harder in the future. Just like doing it right once. Hard to do when everyone seems to differ on the right parts. Upgrades will surely be made. Just deciding which one to go with.

 

TTT for more which input to go with please.

 

this has me scared that I should have done a hardened input shaft in my 80E with my heavy truck

 

There are some decent billet shafts out there from several vendors now.
We've seen some that broke. I'll say they we're made in North America but not the US and leave it at that.

The CK shaft is probably a decent piece. I had some issues with CK parts quality control int he past and quit using them several years ago (5-6 yrs ago now). Like stated above, the termination of the splines isn't a weak point.

We are using some shafts now that are undercut on purpose

 

And definitely do the input shaft, forget the mainshaft unless you are running 1000+ HP or big shot of N2O off the line on sticky tires.