SHELBY GT 350 Member
Joined: Sep 2010
Location: see user name
My only thought is the preload is off. But generally you'll know that due to whining noise on either decel or accel - I forget which is which, but whining on decel would be indicative of too much, and on accel would be too little. Or vise-versa, cause like I said I'm a bit mixed up on that and don't have the exact info right in front of me.
There are also two methods or tq specs for tightening the pinion nut - 1st is to reinstall it with the exact same amount that it took to remove (assuming there were no prior related preload issues); 2nd is more of a "virgin" tq spec - it's in lb/in spec, if you have a Haynes manual then I'm sure you're familiar with it since you've already been through this a couple times.
But assuming no whining from incorrect preload, then I'm drawing blanks here.
2001 GT Convertible
All the usual bolt-on's /200 I6, C4
And a few Explorers too... 2008 4.0 XLT 4x2, 1996 XLT 5.0 4x2, 2003 Sport Trac XLT 4.0 4x4