Axle swap question

[jamezz]

Before swapping the axles out on my K5 to 3/4 ton with a 14b ff. I did a lot of reading and found in doing so I would have to shorten the drive shaft. After my swap I had to lengthen my by 1/2 of an inch. Why would this be?
88 k5 350, 700r and 208 tc. Rear 14b came out of a 75 k20. Everything works fine but I'm just wondering after all I read why would I have to lengthen it. Unless there's something I'm missing. This was my first axle swap.

 

[83ChevyK5Blazer]

Any lift?

 

[jamezz]

Any lift?

The time of the swap I had a two inch lift. It was the same lift with both axles when measuring and during the swap. 2-in block anyways.

 

[nvrenuf]

The 14 bolt has a pretty short pinion gear, I’d bet it’s shorter than a 10 bolt (what you took out).