What's the minimum safe inward clearance? Driveshaft builder thinks I can get away with 3/4". I was going to get 1/8" cut off and a 1" counterbore to allow for 1". Or just do the 1" counterbore to get 3/4" to 7/8" of clearance and save a bit more spline. Rear suspension is dropped 3".

 

Grant it almost looks like that shaft has been machined down to allow a long spline yoke to work. I could be wrong but it looks like it was not machined far enough. In your original unit the long spline output in my opinion is really the way to go. I would ask your builder if he machined your current output down and if possibly it was not done far enough. Feel free to pm if needed. Vince

 

I machine shafts similar to that often. There is ~2.75" of spline on the shaft as I recall. The machined area is about 1".

If you slide the yoke until it bottoms, withdraw 1", you have complete spline engagement and 1" of inward travel for suspension movement. If you need more than 1" of movement, you need to do something different with the driveshaft (2 piece with carrier bearing and plenty of travel).

2" of splined engagement will handle more power than most will ever see, and likely more than the OEM output shaft would anyway.

 

I was concerned with lateral stability. I noticed that there is a little lateral play/rock on the splines while holding the output shaft stable. Cutting off the required 1" would have left only 1/2" of yoke through the bushing. So I had the yoke counterbored 1". Machining another 1" of the shaft would have accomplished the same thing. I was just barely able to squeeze the rear u-joint past the flange to get it seated. There is now 15/16" of forward room. A full spline shaft would still be my first choice.



Resting position



Full Forward



Rest



New Loop

 

At full suspension droop it pulls out 1/2" so I still have 1" through the bushing and 2.25" of spline engagement.

 

Glad you got it figured out!!!