"pinyon" Seal. You'll need to pull the pinyon flange to get to it so be prepared to use a long Cheater bar and a 6 point socket...I believe the flange nut is staked so its best to get a new one. Pay close attention to the the torque spec when re-installing the flange nut.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..