It never leaked before, my guess it that they put a jack under it and it busted the seal loose
is it leaking from the cover gasket, or the pinion seal up at the shaft?
that's what I figured with it getting on the car behind you...
Plus I quite a few nibs ...I am afraid to de-nib it...
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dust in the paint? was it cut/buffed?
oh, and ummm, gotta look at the failure point..
I would guess the yoke is flinging it around maybe... check the floor above it too...
they usually wouldn't "blow out" unless you had a blocked vent or something... probably started a long time ago...

I know what you mean. Just put it together and drive it.
Count the cover bolts. You should have a 12 bolt rear, 8.875". There is no 8.125" diff. 8.875" is the early diff, 8.5" is the later diff.
MasterPro® Bearing/Seal - Pinion Seal
1 Year Limited Warranty
Rear Outer
8.125 Inch Ring Gear
Quantity Per Vehicle: 1
For Pricing
& Availability,
enter your zip code.
Part # : 8611N | Line: MPS
PowerTorque® - Differential Pinion Seal
PowerTorque® - Differential Pinion Seal
Limited Lifetime Warranty
Rear
GM 9.5 Inch
Second Design
Quantity Per Vehicle: 1
For Pricing
& Availability,
enter your zip code.
Part # : 743B070A | Line: PTQ
National® - Pinion Seal
National® - Pinion Seal
1 Year Limited Warranty
Multiple Applications
Rear Outer
- 8-7/8 Inch Ring Gear
Rear Outer
- GMC Axle
- 8.875 Inch Ring Gear
Quantity Per Vehicle: 1