1998 F-150 4x4, Rear end growl is getting worse and I am showing an abs and a brake warning lights. Am I better off re building my rear dif or should I try to find a used rear end. Just got the truck and I can see that the cover has been leaking and has been removed a few times. Need advice

 

Rebuild it unless you have a free or rediculously cheap replacement available. Good luck!