Recently drove my 99 7.3 duelly f350 on dry roads with 4-hi and hubs locked...
Realized what I had done once I was forced to the side of the road by very loud grinding and clanking.
I have replaced the oem manual locking hubs with warn locking hubs but when I lock them the whole axle locks solid, like the wheels won't spin at all when gas is applied( scared to applied too much gas and break something else).
Anyone else experience this and have some advice for me?

 

Sounds like the differential is toast. Pop the diff cover and see how many pieces fall out.

 

I didn't think Of that. Ill have to check that out tomorrow or something. Its raining and dark out and I dint have a nice place to work.

 

Would the differential still be your assumed suspect if I told you the truck drives fine in 2wd and 4x4. Only when you lock the hubs it binds up solid.

 

You can run the tcase in 2 or 4 with no binding until hubs are locked? If that's the case, I'd suspect an axle joint that's toast, but would cause the bind in turns.

 

It binds right away with wheels turned or straight doesn't matter. Lock the hubs=not even full wheel rotation until it binds.

 

I'd check axle u joints first then.