The wet-end seal stack for the GP5132 — everything from the crosshead pin through the plunger bore seals. This group contains the highest-frequency wear parts in the pump: O-rings, grooved rings, case seals, pressure rings, V-sleeves, and the seal sleeve, along with the structural plunger pipe, tensioning hardware, and oil scraper.

These are the parts that go into a plunger repack. If pressure is dropping under load without obvious valve damage, a worn plunger seal stack is the most common cause. The GP5132 Packing Plunger Kit covers the full repack in a single order — source individual components here when only part of the seal stack needs replacing.