Conversation Between TexasRebel and Puckhog

Happy New Year!

Splines are incredibly strong! The splines might seem small, but they all take an equal load. They also get strength with engagement length.

For future drive line work, it may be easier to put the transmission/t-case into neutral and let the shaft turn freely than to try to position the pinion yoke to the shaft. Always set chocks and use jack stands! For that particular job it's best to rest the frame on jack stands with the axle hanging then lower the axle than to try to raise the pickup off of a disconnected axle.

We just got a bit of snow! Hopefully your weather isn't getting too bad.

I will say this much however . . . I am absolutely amazed (no, stunned!) that the entire drivetrain for this reasonably heavy truck is dependent on that single, relatively small set of splines on the front of the driveline. You would think that the immense torque applied by a whopping 6.7L diesel motor would spin the splines right off of a shaft that small and fragile in nature. That part simply amazes me! Wouldn't you think they'd want to couple those two parts with something far sturdier than a single, fine-toothed shaft like that??

Anyway, thanks again for providing me with the assistance that you did. I'm most grateful. And Happy New Year to you!

However, like an idiot, when I jacked-up the truck to remove the stock F350 blocks, I failed to chock the two front wheels, and without my knowing just how it was all designed, the vehicle rolled forward about 4-inches and the front spline of the drive shaft slipped out of the yoke in the slip joint, resulting in misalignment of the two parts.

Anyway, to make a long story short, I disconnected the rear half of the driveline from the rear differential to help make alignment of the spline with the slip joint yoke possible, and when I did so (i.e., once I had the driveline completely detached from the rear end), the front spline slid right into place the way it was supposed to. I then turned the wheels until the holes for the four 12mm bolts that attach the rear of the driveline to the differential lined-up, and everything then worked out just fine. I reinstalled the 4 bolts with lock-tite and torqued the 8 new u-bolt nuts at the rear end, and shazam!

TexasRebel,

My thanks for your excellent contributions to this thread and for this detailed message, and please accept my sincere apologies for the delay in responding to it. Unfortunately, I just now discovered it (today on January 8th), after having some computer problems and being logged-off of the forum.

Anyway, to answer your question and help update you on just what happened with this ordeal . . . this whole thing started with my desire to level this new F350 by dropping the overall height of the rear-end by 2-inches. I simply wanted to replace the 4" tall rear leaf spring blocks that come standard on F350s with the shorter (2-inch tall) F250 blocks. Seems simple enough, right? And it certainly should have been! (SEE PART 2 OF MESSAGE TO FOLLOW).

Replied! Hope it helps.

Did you take all of these parts off, or are you replacing parts with other parts.

The spline you describe is what is called a "master spline", and it is used to align shafts that need it. A 1-piece drive shaft with a slip-spline in the middle would need to be clocked. A 2-piece drive shaft would not. The two directions to try first would be to align the yoke on the female spline with the yoke on the shaft with the male spline. If it doesn't fit, turn it 180 degrees and try again. If neither of these work, try turning it 90, trying again, then 180 and trying again. Past that you'll just have to try each tooth until it fits...

If the external spline has a master spline and the internal does not... they will never go together.

Greetings, Texas Rebel!

I'm a new forum member, and I'm having a bit of trouble determining the proper alignment and installation of the front spline on the rear driveshaft of a 2015 F350. I've posted a new thread on it here this morning, and I see from some earlier related threads that you might have experience on this subject. If so, and if you're willing to provide me with any opinions or guidance, I'd sure appreciate it. The new thread is located at:

https://www.ford-trucks.com/forums/1...l#post15875305

Either way, my thanx to you for listening and Happy Holidays!