hey all. 2002 f350 dually 7.3 6sp. 125000 miles just started making a grinding noise when accelerating. happens in all gears. not when idling. lock in front hubs and noise goes away. i removed, cleaned, greased, and inspected lock outs. all looked to be in order. reinstalled and same noise when in free. sounds like two plastic gears stripping each other out. lock hubs and it stops making noise. when the hubs are unlocked and the truck is making the noise, if i put it in 4wd, the noise stops. nothing unusual looking under front end. u-joints are tight.the truck drives normal when the hubs are locked or when it is in 4wd. unlock the hubs and put it in 2wd and the grinding begins when under a load. i will be checking fluid levels in the t-case and front diff today. as usual, any help is appreciated.

i removed the front drive shaft and took it for test. no noise. aparently i was too easy on it in the subdivision. tried the highway and the same old grinding sound. back to square one. ??

 

Are they locking hubs only or do you have the electronic switch also?

 

A dry u joint will feel tight , but can produce grinding squealing noises when under load. You may need to drop the entire rear driveline and feel for any roughness in the u joints and center brg if it has one.