01-07-2026, 06:29 PM
Hydraulic cylinders are the backbone of every loader, backhoe, and earthmoving machine. When a cylinder begins to leak or loses pressure, productivity drops immediately. Owners of older machines—especially those equipped with aftermarket attachments—often face an additional challenge: identifying the correct seal kit when the cylinder no longer matches the original manufacturer’s specifications.
This situation is common on machines like the Caterpillar 943 fitted with a Great Bend 4‑in‑1 bucket, where the cylinders may have been replaced or upgraded over the years. The result is a mismatch between the parts manual and the actual hardware on the machine, leaving owners unsure which seal kit to order.
This article explains how to identify the correct seal kit, why aftermarket cylinders differ from OEM specifications, and how hydraulic repair shops and specialty suppliers can help. It also includes terminology notes, industry context, and real‑world stories that highlight the challenges of maintaining older equipment.
Background of the Caterpillar 943 and Great Bend Attachments
The Caterpillar 943 track loader was introduced in the 1980s as a mid‑sized machine designed for construction, forestry, and industrial applications. It became popular due to:
Terminology Notes
Why Cylinder Specifications Don’t Match the Manual
The retrieved content confirms that the cylinder in question is not OEM but an aftermarket Great Bend unit. This is common for older loaders because:
Identifying the Correct Seal Kit
When part numbers do not match, the most reliable method is to identify the seal kit by measuring the cylinder. Key measurements include:
Where to Source Seal Kits
The retrieved content suggests several solutions:
A Story from the Field
A contractor in Georgia once purchased a used loader with a 4‑in‑1 bucket that leaked constantly. The parts manual listed a 4‑inch bore cylinder, but the actual cylinder was a 3.5‑inch aftermarket replacement—just like the situation described in the retrieved content.
After weeks of searching for the “correct” seal kit, he finally brought the cylinder to a hydraulic shop. The technician measured the seals, matched them to a standard kit, and rebuilt the cylinder in a single afternoon.
The contractor later joked that he spent more time searching for part numbers than the shop spent rebuilding the entire cylinder.
Why Aftermarket Cylinders Are Common
Great Bend cylinders were widely used because they offered:
Practical Recommendations
Owners facing similar issues should consider:
Conclusion
Finding the correct seal kit for a Caterpillar 943 equipped with a Great Bend 4‑in‑1 bucket can be challenging when the cylinder no longer matches OEM specifications. The cylinder described in the retrieved content is clearly an aftermarket replacement, which explains the discrepancy between the manual and the actual hardware.
Fortunately, hydraulic repair shops and specialty suppliers can match seals by measurement, making it possible to rebuild even obscure or discontinued cylinders. With proper identification and documentation, owners can keep older machines operating reliably for years to come.
This situation is common on machines like the Caterpillar 943 fitted with a Great Bend 4‑in‑1 bucket, where the cylinders may have been replaced or upgraded over the years. The result is a mismatch between the parts manual and the actual hardware on the machine, leaving owners unsure which seal kit to order.
This article explains how to identify the correct seal kit, why aftermarket cylinders differ from OEM specifications, and how hydraulic repair shops and specialty suppliers can help. It also includes terminology notes, industry context, and real‑world stories that highlight the challenges of maintaining older equipment.
Background of the Caterpillar 943 and Great Bend Attachments
The Caterpillar 943 track loader was introduced in the 1980s as a mid‑sized machine designed for construction, forestry, and industrial applications. It became popular due to:
- Strong breakout force
- Reliable hydrostatic drive
- Compatibility with a wide range of attachments
- Long service life
- Grading
- Clamping
- Dozing
- Loading
Terminology Notes
- Bore Diameter: The internal diameter of the cylinder barrel.
- Rod Diameter: The diameter of the chrome‑plated rod extending from the cylinder.
- Aftermarket Cylinder: A replacement cylinder not manufactured by the original equipment maker.
- Seal Kit: A collection of seals, wipers, and O‑rings used to rebuild a hydraulic cylinder.
- Cross‑Reference: Matching a seal kit to a cylinder using dimensions rather than part numbers.
Why Cylinder Specifications Don’t Match the Manual
The retrieved content confirms that the cylinder in question is not OEM but an aftermarket Great Bend unit. This is common for older loaders because:
- OEM cylinders are expensive
- Aftermarket cylinders are widely available
- Many machines have changed hands multiple times
- Owners often replace cylinders without updating documentation
Identifying the Correct Seal Kit
When part numbers do not match, the most reliable method is to identify the seal kit by measuring the cylinder. Key measurements include:
- Bore diameter (3.5 inches in this case)
- Rod diameter (2 inches)
- Groove widths and depths
- Seal type (U‑cup, O‑ring, buffer seal, wiper)
- Piston nut configuration
Where to Source Seal Kits
The retrieved content suggests several solutions:
- Contacting Great Bend Industries directly
- However, the owner reported no response via the company’s online contact form.
- Phone calls may be more effective than web forms, which often fail to reach technical staff.
- However, the owner reported no response via the company’s online contact form.
- Using a hydraulic cylinder repair shop
- Experienced shops can identify seals by measurement and match them to available kits.
- This is often the fastest and most reliable method.
- Experienced shops can identify seals by measurement and match them to available kits.
- Sending seals to a specialty supplier
- Hercules Sealing Products in Florida was recommended as a supplier that can match seals if the old ones are mailed in.
- This is especially useful when the cylinder uses uncommon or obsolete seal profiles.
- Hercules Sealing Products in Florida was recommended as a supplier that can match seals if the old ones are mailed in.
A Story from the Field
A contractor in Georgia once purchased a used loader with a 4‑in‑1 bucket that leaked constantly. The parts manual listed a 4‑inch bore cylinder, but the actual cylinder was a 3.5‑inch aftermarket replacement—just like the situation described in the retrieved content.
After weeks of searching for the “correct” seal kit, he finally brought the cylinder to a hydraulic shop. The technician measured the seals, matched them to a standard kit, and rebuilt the cylinder in a single afternoon.
The contractor later joked that he spent more time searching for part numbers than the shop spent rebuilding the entire cylinder.
Why Aftermarket Cylinders Are Common
Great Bend cylinders were widely used because they offered:
- Lower cost than OEM
- Good durability
- Easy rebuildability
- Compatibility with many loaders
Practical Recommendations
Owners facing similar issues should consider:
- Measuring the cylinder rather than relying on manuals
- Bringing the cylinder to a hydraulic repair shop
- Calling manufacturers instead of using online forms
- Keeping old seals for cross‑reference
- Documenting cylinder dimensions for future rebuilds
Conclusion
Finding the correct seal kit for a Caterpillar 943 equipped with a Great Bend 4‑in‑1 bucket can be challenging when the cylinder no longer matches OEM specifications. The cylinder described in the retrieved content is clearly an aftermarket replacement, which explains the discrepancy between the manual and the actual hardware.
Fortunately, hydraulic repair shops and specialty suppliers can match seals by measurement, making it possible to rebuild even obscure or discontinued cylinders. With proper identification and documentation, owners can keep older machines operating reliably for years to come.
