Unless it is leaking, leave it alone. You will have to remove the pinion flange and retainer nut, which will kill the bearing preload on the pinion shaft. Torque and position of these components is critical to proper rear end setup and clearances. Don't fix it if it "ain't" broke.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.