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355-7377 CAT 988K / 988K XE Lift Cylinder (RH) Aftermarket Replacement
355-7377 CAT 988K / 988K XE Lift Cylinder (RH) Aftermarket Replacement
Lift Cylinder (Right-Hand) for Caterpillar 988K / 988K XE Wheel Loader.
- OEM Part Number: 355-7377 / 3557377
- Left-hand pair: 355-7378
- Bore × Rod: 210 mm × 130 mm
- Cat seal kit: 477-9286 (standard size)
- Serial prefixes: 988K L8X, LWX, T8E, TWX · 988K XE E8X
- Weight: approx. 690 kg (shipping)
- Fitment: Direct drop-in replacement — no machine modification required
- Warranty: 12 months / 2,000 hours
Product Overview
SEIGO’s aftermarket lift cylinder, part number 355-7377, is a direct drop-in replacement for the right-hand lift cylinder on the Caterpillar 988K wheel loader and the diesel-electric 988K XE. The 988K is Caterpillar’s large production loader for quarry face loading, aggregate stockpiles and mine-site truck loading. The lift cylinder has a 210 mm bore and a 130 mm rod, and it is fitted to machines with serial prefixes L8X, LWX, T8E and TWX (988K) and E8X (988K XE).
The 988K uses a pair of lift cylinders, one on each side of the loader linkage. 355-7377 is the right-hand cylinder; the left-hand cylinder is 355-7378. Both share the same bore and rod dimensions and the same Cat seal kit, 477-9286, but porting and mounting differ between sides, so the hand must be correct when ordering.
On a production loader, the lift cylinders carry the full weight of the loaded bucket through every lift cycle, hundreds of times per shift. The dominant failure modes are rod chrome scoring from abrasive dust at the loading face, rod seal leakage once the chrome is damaged, and lift drift from internal piston seal bypass. Because both lift cylinders accumulate identical hours, a failure on one side is a strong signal that the other is close behind.
SEIGO manufactures the 355-7377 to full Caterpillar dimensional specification: a 42CrMo4 induction-hardened, hard-chrome-plated piston rod at 130 mm diameter, an ST52 seamless honed steel barrel machined to the 210 mm bore, and a genuine NOK (Japan) or Parker (USA) seal kit matched to the Cat 477-9286 seal layout. Every unit is pressure tested at 1.5× rated working pressure before shipment from our Guangdong factory and is backed by a 12-month or 2,000 operating-hour warranty. Standard lead time is approximately 30 days ex-works, with expedited production available for machine downtime.
Product Specifications
| Product category | Hydraulic Cylinder |
| Machine type | Large Wheel Loader |
| Machine brand* | Caterpillar |
| Compatible models* | 988K, 988K XE |
| Serial prefixes* | 988K: L8X, LWX, T8E, TWX · 988K XE: E8X |
| Cylinder type | Lift Cylinder (loader boom lift) |
| Hand | Right-Hand (RH) |
| OEM part number* | 355-7377 (3557377) |
| Left-hand equivalent* | 355-7378 |
| Cat seal kit* | 477-9286 (standard size) |
| SEIGO part number | SG3557377 |
| Bore diameter | 210 mm |
| Rod diameter | 130 mm |
| Stroke / pin-to-pin length | Confirmed against your machine serial number at quotation |
| Rod material | 42CrMo4, induction hardened, hard chrome plated |
| Barrel material | ST52 seamless honed steel tube |
| Sealing system | NOK (Japan) or Parker (USA), matched to Cat 477-9286 seal layout |
| Design option | Standard specification, or cold climate specification (−40°C / −50°C) |
| Approx. weight | 690 kg (shipping weight) |
| Testing | 100% pressure tested at 1.5× rated working pressure |
| Certification | ISO 9001:2015 certified manufacturing |
| Shipping | ISPM-15 fumigated wooden export crate |
| Manufactured in | Guangdong, China |
| Lead time | Approximately 30 days ex-works; expedited production available |
| Incoterms | FOB Shenzhen / CIF / DDP |
| Warranty | 12 months / 2,000 hours, whichever comes first |
| HS code | 841221 |
* OEM part numbers, brand names and model designations are used for identification and cross-reference purposes only. SEIGO Machinery is an independent aftermarket manufacturer and is not affiliated with Caterpillar Inc.
Cat 988K Lift Cylinder Cross-Reference
The 988K and 988K XE use a pair of lift cylinders that share the same bore, rod and seal kit. Part 355-7377 is the right-hand cylinder.
| Part Number | Hand | Bore × Rod | Machines / Serial Prefixes |
|---|---|---|---|
| 355-7377 | Right (RH) | 210 × 130 mm | 988K (L8X, LWX, T8E, TWX); 988K XE (E8X) |
| 355-7378 | Left (LH) | 210 × 130 mm | 988K; 988K XE (E8X) |
Cat Seal Kit 477-9286 — Component Reference
Caterpillar services this lift cylinder with seal kit 477-9286 (standard size). Its catalogued components confirm the 210 mm bore and 130 mm rod:
| Cat P/N | Component | Size |
|---|---|---|
| 374-9649 | Lift cylinder wiper seal | — |
| 172-3918 | Two-piece piston seal | 210 mm bore |
| 265-9690 | Rod guide | 130 mm ID |
| 155-9098 | Backup ring | — |
| 374-9650 | U-cup rod seal | 130 mm |
Seal kit 477-9286 is also listed by Caterpillar for the current-generation 988 and 988 XE. Whether the complete cylinder 355-7377 fits a current-generation 988 must be confirmed against the machine serial number. SEIGO supplies the complete cylinder, the seal kit, and individual rod, barrel and head components for this position.
Cat 988 Generations — Lift Cylinder Reference
Each 988 generation uses a different lift cylinder with different dimensions. Ordering by model name alone is a common source of wrong-part orders.
| Generation | Lift Cylinder Part Numbers | Rod × Bore |
|---|---|---|
| 988K / 988K XE | 355-7377 (RH) / 355-7378 (LH) | 130 mm × 210 mm |
| 988H | 173-8612 / 173-8613 | 5 in × 220 mm |
| 988G | 230-9366 / 230-9367 / 230-9368 | 4-1/2 in or 5 in × 220 mm |
| 988F / 988F II | 9T-8257 | 4 in × 8-1/2 in |
Lift cylinders do not interchange between 988 generations. The 988K moved to a 210 mm bore with a 130 mm rod; the 988G and 988H used a 220 mm bore. Confirm your machine serial number before ordering. SEIGO manufactures lift, tilt and steering cylinders across the 988 range.
Why This Cylinder, Specifically
- Correct hand, verified. 355-7377 is the right-hand lift cylinder; 355-7378 is the left. Porting and mounting differ between sides. We confirm the side against your serial number before quoting.
- Built to the Cat seal layout. 210 mm bore and 130 mm rod, machined to accept the same seal layout as Cat kit 477-9286, so the cylinder can be resealed with standard kits for its whole service life.
- Abrasion-rated rod. Rod chrome scoring from loading-face dust is the leading failure initiator on a 988K. We specify 42CrMo4 with a hard chrome finish chosen for scoring resistance, because rod condition sets the seal interval.
- Replace as a pair. Both lift cylinders share identical operating hours. We supply matched RH (355-7377) and LH (355-7378) cylinders on a single order to keep lift balanced and avoid a second shutdown.
- Rebuild instead of replace. For workshops with in-house assembly, we supply the rod, honed barrel, cylinder head, piston and seal kit individually — typically 40–60% of the cost of a complete cylinder, with far lower freight than a 690 kg assembly.
- Full traceability and testing. ISO 9001:2015 manufacturing, 100% pressure tested at 1.5× rated working pressure, shipped in an ISPM-15 fumigated export crate with material certificate and test record.
FAQ
Q1: Is 355-7377 the left-hand or right-hand lift cylinder?
A: 355-7377 is the right-hand (RH) lift cylinder for the Cat 988K and 988K XE. The left-hand cylinder is 355-7378. Both have a 210 mm bore and 130 mm rod, but porting and mounting differ by side, so confirm which side you need before ordering.
Q2: What are the bore and rod dimensions of 355-7377?
A: The cylinder has a 210 mm bore and a 130 mm rod. These dimensions match Caterpillar seal kit 477-9286, whose catalogued components include a 210 mm piston seal and a 130 mm rod guide and U-cup. For an unmarked cylinder, measure the barrel and rod outside diameters and send us the pin-to-pin length so we can confirm the part.
Q3: Does 355-7377 fit the 988K XE?
A: Yes. Seal-kit catalogue data lists 355-7377 (RH) and 355-7378 (LH) for the 988K XE with serial prefix E8X, in addition to the standard 988K prefixes L8X, LWX, T8E and TWX. Send us your full serial number and we will confirm fitment.
Q4: Will a 988H or 988G lift cylinder fit my 988K?
A: No. The 988H and 988G lift cylinders use a 220 mm bore and different part numbers (173-8612 / 173-8613 on the 988H; 230-9366 to 230-9368 on the 988G). The 988K uses a 210 mm bore with a 130 mm rod. Confirm the machine generation from the serial number before ordering.
Q5: Can I buy the seal kit, rod or barrel separately?
A: Yes. SEIGO supplies seal kits matched to the Cat 477-9286 layout, as well as the piston rod, honed barrel, cylinder head and piston as individual items. For workshops rebuilding in-house, sub-component supply typically runs 40–60% of the cost of a complete cylinder. Send us your serial number and the component you need for a quotation.
Q6: What is the lead time and how does it ship?
A: Standard production lead time is approximately 30 days ex-works Guangdong, China, with expedited production available for machine downtime. At approximately 690 kg shipping weight, each cylinder ships in an ISPM-15 fumigated wooden export crate, FOB Shenzhen, CIF or DDP.
SEIGO Machinery is an independent aftermarket manufacturer. All OEM part numbers, brand names and machine model designations are used for identification and cross-reference purposes only. These aftermarket components are not manufactured by, endorsed by, or affiliated with Caterpillar Inc.
