Currerently out at the dunes and was climbing up a huge dune when I heard a clunk and lost 4wd. I backed it down in 2wd and inspected. I noticed the front driveshaft is still spinning but no power to the front wheels.

I drove it back to camp with a moderate clunk in the front drive line somewhere. The half shafts are in good shape along with the front d shaft. Which you turn the front shaft by hand you can see a bit of play and movement towards the inside of the front diff area past the front CV on the drivers side. This is also where I hear the clunk when driving.

So we believe the inner shaft is broken. Can you drive on it like that? I'm afraid of grenading it on the 170 mile trip home.

Are there any other possibilities for the issue? Thanks.

 

If you're worried about busting it just take the front prop off.

Are you sure that it's actually broken inside? The front driveshaft will spin at all times (in 2 and 4wd) It's possible that the linear actuator broke/partially disengaged.

 

Here's a video of the event. It's fairly boring:

Silverado broken axle on test hill at Silver Lake - YouTube

It also is sort of inconclusive due to the fact it appears that the 4x4 is working after the clunk. It's getting tore apart today and I'll update with pix.

 

Depending on what tools you have available, you can pull the CV's apart and leave the stub installed in the spindle (wheels will fall off without that part) but remove the rest of it, then if you were to remove the front driveshaft as well, the front diff would not be turning at all.

 

Well I ended up tearing it apart. Got a bunch of videos of the disassembly that Ill post later after my buddy sends me them.

This is the video of me trying to move the axle around with 4x4 engaged:

Axle slop - YouTube

I disassembled the half axle on the passenger side along with the front axle engagement assembly and it had some gunk in it from what appeared to be excess RTV.

I cleaned and reassembled and re-engaged 4x4 to see if the skipping action went away. It didn't so I assume:

1. somethings not installed correctly or
2. the actuator is bad and is only partially engaging and partially disengaging the axle (despite it appearing to move completely in and out when being ran outside of the axle housing) or
3. something else is up...

I did push a socket handle as hard as I could into the actuator location and I was still getting the slippage. Maybe its normal? Maybe its not? I don't know.

I'm likely going to pull the whole diff assembly and see whats inside.

 

This will tell you pretty much anything you want to know about taking a front diff apart:

The Official GMFS Front IFS Gear Install How-To - Chevy Truck Forum | GMC Truck Forum - GmFullsize.com

I'm wondering if you have a broken ring or pinion gear.

 

I turned the diff assembly with the pass side axle housing off and its smooth as butter. I did notice some clunking/loose soemthing sounds when turning the front driveshaft with it in 2wd. I forgot to put it back into 2wd and turn the front driveshaft with the passenger side housing and axle actuator assembly out, so I'll have to do that tomorrow.