Grinding gears? Sticky shifter? A gearbox caked in grease will lead to massive maintenance headaches.
Excess grease buildup causes friction, heat, and wear, significantly shortening the life of your gearbox components.
Follow our simple 6-step guide to safely and effectively clean grease from your gearbox. A few hours of elbow grease now will keep your machinery running smoothly for years to come.
Step 1: Disassemble the Gearbox
Begin by draining any oil or fluids from the gearbox. Then, carefully remove the gearbox cover, taking note of the position and orientation of each component. Extract the gears, bearings, seals, and shafts, keeping related parts together. Consult the gearbox service manual for specific disassembly instructions for your model.
Step 2: Remove Excess Grease
With the gearbox fully disassembled, use a putty knife, scraper, or rag to manually remove as much of the old, contaminated grease as possible. Pay special attention to corners, crevices, and blind holes where grease tends to collect and harden over time.
However, avoid using abrasive tools or excessive force, which may damage the precision-machined surfaces of gears and bearings. If the grease is particularly hardened, soak the parts in a petroleum-based solvent for several hours to soften the deposits before scraping.
Step 3: Select a Solvent
To dissolve the remaining grease, you’ll need to select an appropriate solvent. The choice of solvent depends on the type of grease in your gearbox and the component materials. Common options include:
General-Purpose Degreasers
- WD-40: A readily available degreaser that can effectively remove grease. It’s important to note that WD-40 is not a lubricant and should be completely removed before applying proper lubricant.
- Isopropyl Alcohol: A strong solvent that can dissolve grease and evaporates quickly. Higher concentrations (91% or stronger) are recommended for better results.
Solvents for Flushing
- Kerosene: A commonly used solvent for flushing gearboxes.
- Mineral Spirits: A safe and effective solvent for removing grease.
Other Solvents
- Naphtha: An effective solvent for removing stubborn grease, especially hardened grease.
- CRC QD Contact Cleaner: A plastic-safe cleaner that can be sprayed on and then removed with a toothbrush.
- Automatic Transmission Fluid (ATF): ATF can be used as a cleaning agent for gearboxes.
- Oil Eater: A non-flammable and non-toxic cleaning agent available at many retailers.
- Oven Cleaner: While effective as a degreaser, oven cleaner should be used with caution as it can damage certain materials if left on for too long.
Step 4: Clean the Components
Place the gearbox parts in a large basin or parts washer filled with your chosen solvent. Use a stiff-bristled brush to scrub the components, paying close attention to teeth, splines, and other complex geometries where grease may persist. For hard-to-reach areas, use a pressure washer or compressed air to blast away deposits.
Soak heavily soiled parts for several hours or overnight if needed. Replace the solvent periodically as it becomes saturated with grease. For large gearboxes with many components, consider setting up a multi-stage cleaning station with fresh solvent in each successive basin.
Step 5: Rinse and Dry
After thoroughly cleaning the parts, rinse them with fresh solvent to remove any lingering debris and contaminated solution. Dry the components immediately to prevent corrosion. Use compressed air, lint-free rags, or place the parts in a low-temperature oven.
Inspect each component under bright lighting to confirm all grease has been removed. Repeat the cleaning process if necessary. Once satisfied, apply a light coat of rust-preventive oil to protect the parts until reassembly.
Step 6: Reassembly and Lubrication
Refer to the service manual and the notes you made during disassembly to reinstall the gearbox components in the correct order and orientation.
As you reassemble the gearbox, apply a thin layer of fresh, high-quality gear oil to each component. Use the viscosity and type of lubricant specified by the manufacturer. Take care not to overfill the gearbox, as excess oil can cause leaks and overheating.
Once reassembled, run the gearbox through its full range of motion to distribute the lubricant evenly. Check for any leaks or unusual noises during operation. If issues arise, disassemble the unit and correct any problems before putting it back into service.
