Seals do wear out over time! They can be replaced fairly easily on the output shaft; if it keeps leaking after replacing with a new seal, you have some other issue...
The pinion seals can also be replaced, but they require a little bit more work to R&R...

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Supporting Vendor and Moderator of LOST05 Jeep Liberty CRD Limited 
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
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Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
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