As the clutch packs wear down, this can open up some play against the spider gears. Are you saying that there is play shortly after rebuilding the 8.8?
How are your u-joints?
As for your pinion leak, it's usually not enough to replace just the seal, which often wears a slight groove into the flange. There are seal-saver kits you can buy that go over the pinion flange, but I think they run about $30, and for just a few dollars more, you can buy a whole new FRPP flange.
1996 Thunderbird LX (4.6), previous daily driver
1995 Mustang GT (5.0), daily driver
1995 GMC C2500 (5.7), alternate daily driver
Last edited by Urambo Tauro; 09-28-2015 at 02:25 PM.