Hey everyone. I have an '85 F-250 that makes a grinding/bearing noise when the hubs are engaged. It can be in 2 or 4 wheel drive and it makes the same sound. Also, both hubs must be engaged for this noise to occur, if only one or the other is engaged it's all good. The 4 wheel stick shift also shakes and vibrates when this noise is occuring. This noise/vibration starts out relatively quiet but by the end of a couple hour trip it's so bad that it rattles things off the dash. Any Ideas???? Thanks for you help!!

 

Grab the front driveshaft and shake it around. See if a u-joint or the splined shaft has wear in it.

 

I messed with the driveline when I first started this whole thing and it seems fine. Plus, even with only one hub engaged the driveline spins, and the noise only occurs with both hubs engaged so I thought I could rule out the driveline as the issue.

 

I've worked on a 93 where the auto lock-outs thought they knew best and kinda stayed half engaged whenever they felt like it and it made a pretty bad sounding noise. We replaced them with manuals for the guy and it fixed right up (manuals were 1/3 of the price). Another thought, how's the transfer case fluid looking? Not saying changing it will help, but if it's discolored it may be a sign of some internal problems, it just seems odd that it gets progressivly worse. My next course of action would be to engage the hubs and remove the front driveshaft and take her for a drive if your having a hard time pin-pointing where the noise is coming from exactly.