O-rings, gaskets, seals

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Always replace O-rings, gaskets and seals.
After removing gaskets and seals, always inspect the contact surfaces at housing or shaft for burrs resulting from removal, or for other signs of damage.
Thoroughly clean housing joint surfaces before assembling.

Fig 1: Identifying Space Between Oil Seal Sealing Lips

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Before installing, lightly oil outer circumference of radial-shaft seals and fill gap between sealing lips - arrow - half way with sealing grease G 052 128 A1 .
The open side of the gaskets points toward the fluid to be sealed in.
Lightly lubricate O-rings before installing, this prevents the rings from being pinched when inserting.
Check transmission oil level after replacing gaskets and seals → Axle oil in rear final drive, checking .