Cat 320C-320E Boom & 323D-330D Bucket Cylinder Seal Kit 2478790 – 85mm Rod x 120mm Bore

Fits Models At A Glance:

• Caterpillar Excavators – boom cylinder: 320C, 320D, 320D FM, 320D FM RR, 320E, 320E L, 320E LN, 320E LRR, 320E RR, 323D L, 323D LN, 323D SA, 323E L
• Caterpillar Excavators – bucket cylinder: 323D L, 324D L, 325D, 325D L, 330D L, 345C L

Key Notes:

• Part Number(s): 2478790 (247-8790)
• Weight: 0.72 lbs (0.33 kg)
• Dimensions: 85 mm rod x 120 mm bore
• Application: Seal kit for the 85 mm x 120 mm cylinder — used as the boom cylinder on the 320-class (cylinder groups 289-7925, 242-6764) and as the bucket cylinder on the 323D L–330D class (cylinder groups 242-6767, 289-7948)
• Serial Number Notes: Cataloged on 320D FM CYZ00001-UP and 320D RR FM SRT00001-UP (boom), 323D L PBM00001-UP (boom) and JLG00001-UP (bucket), 324D L JJG00001-UP (bucket), 325D L MCL00001-UP, GBR00001-UP, GPB00001-UP, PKE00001-UP (bucket), 330D ERN00001-UP and THJ00001-UP (bucket). Same kit, two jobs — confirm your cylinder is 85 mm rod / 120 mm bore.
• Manufacturer: Also supplied as Hercules CTC-2478790
• Condition: Aftermarket replacement part

Common Use Case or Symptoms:

Use when the 320D boom settles or the 325D/330D bucket drifts and the cylinder rod streaks with oil on the 85 mm x 120 mm cylinder.

Why Choose Broken Tractor:

• ✅ One kit, two cylinders — Cat uses the same 85 x 120 cylinder as a boom cylinder on the 320s and a bucket cylinder on the 325D/330D — we spell that out so nobody orders the wrong job.
• ✅ Cylinder groups and serial prefixes listed — Four Cat cylinder groups and their books are named above.
• ✅ ready to ship from our U.S. warehouses — Louisiana and Ohio.