Hi all , really stumped ?!? I have a 2010 f150 stx4x4 , recently started noticing rear end shake/ shudder from stop to slow turns. Did some research, cluthes going bad not slipping. Solution : try changing fluid and adding friction additive and or replace clutch packs !? So checked my door jamb to verify LS rear end it says B6 = 3.73 ls?! When I pop off axle cover I see no “s” spring ??!! Also there are no tags on the axle cover bolts to verify anything ?!? Confused I continue on changing the fluid. Seal it all up take it for a drive no shudder ?!?! Decided to jack up rear end and spin wheels to check if open or ls ! Wheels spin opposite direction ?!?!? So what do I have going on. ? Is the rear end an open diff or are the clutches completely gone and acting as if it is open. Is the lack of that spring mean it’s an open diff ? Would an open diff have that shake/shudder ? Is the door jamb sticker wrong !?!? Any help or insight ?!? Thanks

 

The 9.75 LS diffs don't have S springs apparently?!! Is yours a 9.75 or an 8.8??!&%^ If the clutches are worn and there's no preload spring the diff will probably act like an open diff with no load on it??? The easy way to be sure if you have a clutch type LSD is to find the clutches in the diff*&^ You can see them!@#$%#@#

Always possible that somebody swapped it. Did you buy it used or new?