I've been having some trouble with my 89 p/u, whenever I engage my hubs or t-case I get a loud kind of howling sound from the front end. Everything still works fine but once I get above 5mph or so it does it. Can anyone shine some light on what might be causing this to happen? I need to get it sorted out asap, it's cutting in to my wheeling trips. Thanks in advance.

 

I'm going to guess it's one of 3 things: a bad CV joint, low fluid in the front diff or a bad bearing in the front diff.