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363-0218 CAT 988K / 988K XE Steering Cylinder Aftermarket Replacement
363-0218 CAT 988K / 988K XE Steering Cylinder Aftermarket Replacement
Steering Cylinder for Caterpillar 988K / 988K XE Wheel Loader.
- OEM Part Number: 363-0218 / 3630218
- Cat description: Cylinder Gp-Steering
- Bore × Rod: 100 mm × 70 mm
- Seal kit: 471-0317
- Serial prefixes: 988K L8X, LWX, T8E, TWX · 988K XE E8X
- Steering circuit: pilot, load sensing — relief 30,000 kPa (4,351 psi)
- Fitment: Direct drop-in replacement — no machine modification required
- Warranty: 12 months / 2,000 hours
Product Overview
SEIGO’s aftermarket steering cylinder, part number 363-0218, is a direct drop-in replacement for the steering cylinder on the Caterpillar 988K wheel loader and the diesel-electric 988K XE. Caterpillar catalogues this part as Cylinder Gp-Steering. It has a 100 mm bore and a 70 mm rod, and is fitted to machines with serial prefixes L8X, LWX, T8E and TWX (988K) and E8X (988K XE).
The 988K is an articulated loader: there is no steered axle, and the steering cylinders do the entire job of turning the machine by pivoting the front and rear frames about the centre hitch through a total steering angle of 86°. The steering circuit is pilot-controlled and load-sensing, fed by a variable displacement piston pump, with a steering relief setting of 30,000 kPa (4,351 psi) on the standard 988K. On a loader cycling between face and truck all shift, the steering cylinders reverse direction on every pass — a high-cycle, high-side-load duty that is quite different from the lift and tilt circuit.
That duty produces a distinct failure pattern: rod chrome wear and scoring from the constant reversing stroke and site dust, rod seal leakage once the chrome is compromised, and wear at the mounting eyes and bearings from articulation side load. A failed steering cylinder takes the machine out of service completely, because an articulated loader cannot be steered safely without it.
SEIGO manufactures the 363-0218 to full Caterpillar dimensional specification: a 42CrMo4 induction-hardened, hard-chrome-plated piston rod at 70 mm diameter, an ST52 seamless honed steel barrel machined to the 100 mm bore, and a genuine NOK (Japan) or Parker (USA) seal kit matched to the 471-0317 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 (articulated) |
| Machine brand* | Caterpillar |
| Compatible models* | 988K, 988K XE |
| Serial prefixes* | 988K: L8X, LWX, T8E, TWX · 988K XE: E8X |
| Cylinder type | Steering Cylinder |
| Cat description | Cylinder Gp-Steering |
| OEM part number* | 363-0218 (3630218) |
| Seal kit* | 471-0317 |
| SEIGO part number | SG3630218 |
| Bore diameter | 100 mm |
| Rod diameter | 70 mm |
| Stroke / pin-to-pin length | Confirmed against your machine serial number at quotation |
| Quantity per machine | Confirm against your parts book (articulated steering) |
| Steering circuit (machine spec) | Pilot, load sensing; variable displacement piston pump, 270 L/min |
| Steering relief setting (machine spec) | 30,000 kPa (4,351 psi) — standard 988K / 988K XE |
| Total steering angle (machine spec) | 86° |
| Rod material | 42CrMo4, induction hardened, hard chrome plated |
| Barrel material | ST52 seamless honed steel tube |
| Sealing system | NOK (Japan) or Parker (USA), matched to 471-0317 seal layout |
| Design option | Standard specification, or cold climate specification (−40°C / −50°C) |
| Shipping weight | Confirmed at quotation |
| 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 Hydraulic Cylinder Cross-Reference
The 988K uses separate steering, lift and tilt cylinders. Part 363-0218 is the steering cylinder; it is a different part from the lift and tilt cylinders and is not interchangeable with them.
| Function | Part Number | Bore × Rod / Stroke | Seal Kit |
|---|---|---|---|
| Steering | 363-0218 | Bore 100 mm × rod 70 mm | 471-0317 |
| Lift RH (standard) | 355-7377 | Bore 210 mm × stroke 1050 mm, rod 130 mm | 477-9286 |
| Lift LH (standard) | 355-7378 | Bore 210 mm × stroke 1050 mm, rod 130 mm | 477-9286 |
| Tilt (standard) | 354-0798 | Bore 269 mm × stroke 685 mm | Confirm by serial |
Cylinder dimensions are taken from Caterpillar 988K machine specifications and seal-kit catalogue data. Confirm your machine serial number before ordering. SEIGO supplies steering, lift and tilt cylinders for the 988K.
Cat 988K Arrangements — Check Before You Order
The 988K is built in a standard arrangement, as the diesel-electric 988K XE, and in special arrangements such as the Millyard (steel mill) loader. The special arrangements use larger lift and tilt cylinders, so the arrangement matters as much as the model name.
| Arrangement | Steering Cylinder | Lift Cylinder (bore × stroke) | Tilt Cylinder (bore × stroke) |
|---|---|---|---|
| 988K standard (L8X, LWX, T8E, TWX) | 363-0218 | 210 × 1050 mm — 355-7377 / 355-7378 | 269 × 685 mm |
| 988K XE (E8X) | 363-0218 | 210 × 1050 mm — 355-7377 / 355-7378 | 269 × 685 mm |
| 988K Millyard arrangement | Confirm by serial number | 235 × 976 mm — 490-7560 / 490-7561 series | 291–292 × 671 mm |
363-0218 is catalogued for the standard 988K and the 988K XE. The Millyard arrangement uses a different steering relief setting (32,000 kPa) and larger work-equipment cylinders, so confirm the steering cylinder number against the machine serial number before ordering for a Millyard or other special-arrangement machine.
Why This Cylinder, Specifically
- Built for articulated steering duty. The steering cylinders reverse on every loading pass and carry side load as the frames articulate. We finish the rod for wear and scoring resistance and specify the mounting bearings for articulation load, because rod scoring and eye wear — not pressure failure — limit service life here.
- Manufactured to Cat dimensions. 100 mm bore and 70 mm rod, machined to accept the 471-0317 seal layout, so steering response and lock-to-lock travel match the original and the cylinder can be resealed with standard kits.
- Correct arrangement, verified. The standard 988K and 988K XE use 363-0218; special arrangements such as the Millyard loader differ. We confirm against your serial number before quoting.
- Safety-critical, tested accordingly. An articulated loader cannot be steered without its steering cylinders. Every unit is pressure tested at 1.5× rated working pressure before it leaves the factory.
- 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.
- One source for the whole loader. SEIGO also manufactures the 988K lift cylinders (355-7377 RH, 355-7378 LH) and tilt cylinder, so steering and work-equipment cylinders can ship on one order.
FAQ
Q1: What are the bore and rod dimensions of 363-0218?
A: The 988K steering cylinder 363-0218 has a 100 mm bore and a 70 mm rod, and is serviced with seal kit 471-0317. Stroke and pin-to-pin length are confirmed against your machine serial number at quotation. For an unmarked cylinder, measure the barrel and rod outside diameters and the retracted pin-to-pin length and send them to us.
Q2: Does 363-0218 fit the 988K XE?
A: Yes. Seal-kit catalogue data lists 363-0218 as the steering cylinder for both the 988K (serial prefixes L8X, LWX, T8E, TWX) and the 988K XE (serial prefix E8X). Send us your full serial number and we will confirm fitment.
Q3: Does it fit a 988K Millyard or steel mill arrangement?
A: Confirm before ordering. The Millyard arrangement uses larger lift and tilt cylinders and a different steering relief setting from the standard machine, and we have not confirmed that it uses the same steering cylinder. Send us the machine serial number and we will verify the correct part.
Q4: What are the warning signs of a failing steering cylinder?
A: Watch for oil weeping at the rod gland, slow or uneven steering, the machine drifting off line, knocking or play at the mounting eyes, and visible scoring on the exposed rod chrome. Because steering is safety-critical on an articulated loader, any of these should be inspected promptly.
Q5: Is the steering cylinder the same as the lift or tilt cylinder?
A: No. The steering cylinder has a 100 mm bore and 70 mm rod. The standard 988K lift cylinders (355-7377 RH, 355-7378 LH) have a 210 mm bore and 130 mm rod, and the tilt cylinder has a 269 mm bore. They are different parts and are not interchangeable.
Q6: Can I buy the seal kit, rod or barrel separately?
A: Yes. SEIGO supplies seal kits matched to the 471-0317 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.
Q7: 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. Each cylinder ships in an ISPM-15 fumigated wooden export crate, FOB Shenzhen, CIF or DDP. Air freight is practical for urgent orders on a cylinder of this size.
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.
