After rebuilding my engine...took some time due to the crazy cost of rebuilding a 5.9 magnum my front axle stripped out the first time I needed to use my 4x4. It turns out that this is a common problem in theses trucks. The front differential has 2 short splined shafts called stub shafts that the cv axles plug into. The female splines tend to rust out on the cv shafts and chew up the soft metal of the stubs shafts in the process.
This is how I fix my problem for about $2
Step 1: Pull the cv and stub shafts
The cv axles are held on by a c-clip a good tug or a pry with a long screw driver should pop them off of the stub shafts.
Don't pull on the end of the axle, you will rip the boots or damage the cv and turn your $2.00 fix into a $200.00 fix quick.
Pull from the end closest to the differential.
Now you can see the stub shafts where they enter the diff.
These are also held in by C-Clips but are a PTA to get out. If you have a slide hammer big enough use it. If not try to pry them out with a large flat head. My slide hammer was not big enough and flat heat did not work. I pulled the cover off the front "needed a cleaning any way" and used a large screw driver to pry between the pinon gear pin and the stub.
The passenger side is long and drivers side is short.
Step 2: Fix em
Im about as cheep as they come and I felt the design was flawed any way.
So I said what the hell I'll weld them, and it works great! over 10,000 miles now with heavy 4x4 use without any problems.
Clean all the rust up and install new clips on the axle side of the stubs to keep them in place while you or your buddy with welding skills sticks them together.
It is important not to get slag on the stubs as the diff seals need a smooth shaft to work. I wrapped mine with painters tape and wet it down a little before welding.
Install the cv axle to the axle stub and weld a good thick bead. Where the cv and the stub mate gives you a nice v grove to lay down a lot of wire or stick.
Don't let the cv get so hot that you melt the boot.
Step 3: Put them back in.
Now the hard part. well it's not that bad really.
Your passenger side stub/cv is gonna be really long. You will need to cut off the bump stop before attempting to install, it wont fit otherwise trust me.
Insert your stub/cv assembly into the diff, give it a good push to seat the c-clip.
Weld your bump stop back on.
Fill your diff back up and re install your knuckles and be on your merry way with a cheap grin on your face.
Save up some money for when your cv's go bad because your gonna need to buy new stubs too. unless like me your rebuild your cv's yourself.