CAT 303.5 Excavator Final Drive Components, Maintenance, and Repairs

Introduction to the CAT 303.5 Final Drive

The Caterpillar 303.5 final drive is an important drivetrain component used in various Caterpillar construction equipment. This robust final drive provides the gear reduction needed to translate engine power into usable wheel torque for traction and working applications.

What is a Final Drive?

A final drive is essentially a gearbox that is positioned at the end of the drivetrain, just before the drive wheels or tracks. It contains a set of gears that provide additional gear reduction to further slow down the rotational speed while multiplying torque.

This allows high engine rpm to be converted into usable low-speed, high-torque output for the wheels or tracks. The overall gear reduction ratio of the transmission and final drive is what determines the machine's pushing, digging, and hauling capability.

CAT 303.5 Excavator Overview

The CAT 303.5 is a popular 5-ton size excavator from Caterpillar. It features a range of configurations including various track and bucket options to suit different applications. Key specs include:

• Operating weight: 10,740 lb (4,875 kg)
• Net horsepower: 58 HP (43 kW)
• Bucket capacity: 0.18-0.85 cu yd (0.14-0.65 cu m)
• Maximum dig depth: 15 ft 2 in (4.62 m)

This versatile, medium-sized excavator is used for various types of digging, trenching, grading, and material handling jobsites. The 303.5 final drive is a key component that allows it to leverage the engine power to perform these tough tasks.

CAT 303.5 Final Drive Specifications

The CAT 303.5 uses a single-stage planetary final drive design. Key specifications include:

• Reduction ratio: 57:1
• Fluid specification: CAT TDTO (Transmission/Drive Train Oil)
• Fluid capacity: 2.1 gal (8 L)
• Input speed max: 2640 rpm
• Max output torque: 14,340 lb-ft (19,440 Nm)

This rugged final drive has a very high 57:1 gear reduction. This allows the excavator's high rpm diesel engine to produce the type of low-speed, high torque output needed for digging bucket force, while also enabling low travel speeds.

Planetary Gear Design

The 303.5 uses a planetary final drive design consisting of a sun gear, ring gear, carrier, and multiple planetary gears. The sun gear is driven by the input power from the diesel engine through the transmission.

This sun gear meshes with and drives the surrounding planetary gears. These planetary gears in turn drive the large ring gear on the outer circumference, which is bolted to the final drive housing, providing the final drive output to the tracks.

This planetary gear arrangement allows high torque gear reduction in a compact, robust package - an important attribute for the confined spaces of heavy equipment.

Maintenance of the CAT 303.5 Final Drive

Like any drivetrain component, proper maintenance is essential to ensure maximum final drive and excavator longevity. Here are key points related to maintaining the CAT 303.5 final drive:

Oil Changes

Regular oil changes help remove contaminants and prevent premature wear. CAT recommends changing the final drive fluid every 1000 hours or annually, whichever comes first. Use only CAT TDTO fluid to factory fill specifications.

Oil Analysis

Oil analysis helps give insight into internal component health. Checking for metal particles and other signs of abnormal wear through oil sampling allows issues to be identified and corrected before failure.

Breather Maintenance

The breather cap and breather passageways should be checked as part of routine maintenance to ensure proper ventilation within the drive housing. A clogged breather can cause excessive pressure and seal damage.

Leak Checks

Frequently inspect the final drive housing, seals, and gaskets for any signs of oil leakage. Repair leaks promptly to prevent oil loss and contamination ingress.

By properly maintaining the CAT 303.5 final drive with regular oil service, leakage checks, and potential issue identification through oil analysis - operators can expect many years of reliable service from this robust final drive.

CAT 303.5 Final Drive Repairs

Even with proper preventative maintenance, repairs may eventually be needed as years of arduous duty take their toll.

Common Failure Points

Some more common things that require 303.5 final drive repairs include:

• Damaged/worn planetary gears
• Cracked/scored bearing journals
• Leaking seals and gaskets
• Excessive noise/vibration

Bearings may also wear over time, allowing too much play between components. Gear teeth can become cracked or break entirely under excessively high torque events.

Repair Options

For minor issues like seals, simple spot repairs may be possible. More significant problems like damaged gears or shafts may require a full final drive overhaul or replacement.

Factory remanufactured and aftermarket replacements are additional options. Repair turnaround times should be considered when evaluating options.

Cost Considerations

A complete new final drive can easily cost $10,000 to $15,000. Remanufactured options help reduce costs. Individual gears or bearings are less but still run several thousand dollars in some cases along with significant labor.

Proper component inspection helps determine the most cost-effective solution on a case-by-case basis.

Conclusion

The CAT 303.5 excavator relies on its rugged final drive to translate engine power into usable traction and digging force. The planetary gear design provides significant torque multiplication from the engine to the tracks in a compact package.

Maintaining fluids, promptly addressing leaks, and utilizing oil analysis helps prevent premature wear and failures in this critical powertrain component. When issues eventually emerge after years of use, both replacement and repair options should be explored to maximize machine uptime.

FAQs

What is the gear reduction ratio of the CAT 303.5 final drive?

The 303.5 uses a single-stage planetary final drive with a reduction ratio of 57:1. This high ratio allows the diesel engine to produce significant torque for excavation work.

What type of oil is used in the 303.5 final drive?

CAT specifies their own TDTO (Transmission/Drive Train Oil) fluid for the 303.5 final drive. This oil meets stringent requirements for friction control, wear protection, viscosity index, and extreme pressure performance.

How often should the final drive oil be changed?

For normal service, CAT recommends changing the final drive fluid every 1,000 hours of operation or annually, whichever comes first. Shorter intervals may be needed for extremely dirty or hot operating conditions.

What are some common failure points of the final drive?

Potential wear items include the planetary gears, bearing journals, seals, and gaskets. Bearings can also deteriorate over time. Significant issues like cracked/broken gear teeth can occur under momentary overload situations or if lubrication fails.