Can you repair a gearbox? Signs, costs, and next steps

Can you repair a gearbox after it begins leaking, running hot, or losing precision? Often times, yes.  

A seal, bearing, or gear can be replaced if the housing remains sound. For maintenance teams, the first signs often appear as oil on the floor, new vibration patterns, or unexplained rises in temperature.  

STOBER evaluates its industrial gear reducers, identifies likely causes of failure, and provides repair and rebuilding services. When a new unit makes the most sense, STOBER can build and ship most gearboxes in one business day. 

When repair makes more sense than replacement 

Damaged gearboxes can be repaired when the internal components are accessible, and the replacement parts can restore the required performance. Assess the damage, parts availability, and lost production costs.  

A seal change, for example, could be straightforward, while a cracked housing or badly damaged gear train can make gearbox replacement the smarter choice. Refer to the following signs and failure analyses to guide your decision-making. 

Common signs of gearbox failure 

Check the sound, temperature, accuracy, and oil condition, then confirm concerns through inspection and measurement. On automated equipment, delayed motion, position errors, or drive alarms are also known to indicate gearbox failure. 

Fluid leaks and contamination 

Photograph the oil around the shaft seals, joints, or plugs, as worn seals let lubricant escape and contaminants enter. Check the oil color and viscosity and analyze suspected water or metal contamination. Read STOBER’s guide on how to select the right gearbox oil for more support. 

Temporary containment can protect the area until shutdown, but it cannot restore lubrication. Follow all OEM limits, stopping for unsafe oil levels or heat before addressing the root cause. 

Overheating and burning smell 

Low oil, improper lubricant viscosity, excessive load, or poor alignment can all increase operating temperatures. A burning smell necessitates an immediate stop and inspection. Compare the temperatures to baseline records, and although thermal imaging can locate hot spots around bearings, seals, and couplings, it cannot determine every root cause by itself. 

Noise, vibration, and mechanical wear 

Grinding suggests gear damage, while rumbling might indicate a worn bearing. Knocks can point to loose parts or damaged teeth. Track the vibration over time and inspect bearings and gears once readings or noise increase. Measure shaft movement and backlash to check for excess play; loss of positioning accuracy in a precision drive can be a clue. 

Electrical and mechatronic faults in automatic gearboxes 

In an automated drive, an encoder fault, drive alarm, or unexpected stop may come from the controls rather than the gearing. Check the fault histories, wiring, fieldbus communication, firmware, and motor parameters before opening the gearbox. ntify complementary components. 

Failure analysis: Repair, rebuild, or replace? 

How much does it cost to fix a gearbox? Cost comes down to the parts, machining, testing, and downtime; compare an itemized estimate to a new unit’s delivered price and service life. 

Root-cause analysis sets the scope. For instance, replacing a failed bearing without correcting misalignment or poor lubrication only invites another failure. Proper repairs target the specific damage; rebuilds renew worn parts to specification. 

Seven-step repair and rebuild workflow 

1. Log the symptoms, operating hours, load, alarms, and photos; inspect the outside for leaks or damage.  

2. Disassemble, clean, organize, and document the condition of each component.  

3. Analyze wear, fractures, oil, and contact patterns to find the failure cause, using metallurgical testing as needed.  

4. Provide a written proposal covering parts, labor, testing, cost, and turnaround.  

5. Replace or machine damaged parts to OEM specifications, using suitable measurements and approved processes.  

6. Reassemble to specified clearances; check alignment, backlash, and balance where applicable.  
7. Run no-load checks and load tests where applicable; document results.  

Typical repairs for precision and automated drives 

The most common gearbox repair work includes replacing seals, bearings, damaged gears, or shafts. Tooth correction or regrinding requires sufficient material and verified tolerances, and severe shaft wear could call for an approved repair or a new shaft. For stainless steel cLEAN systems, confirm water ingress and washdown compatibility when choosing parts. 

Automated systems might also need a new sensor, actuator, or drive component. It’s best to test motor and controls before replacing uncertain hardware. 

When a new gearbox is the better choice 

Strong signs that replacement may be the better choice include cracked housings, widespread tooth damage, obsolete parts, or a repair quote that nears the replacement cost. Compare the efficiency, fit, expected service life, and future maintenance costs, too. STOBER offers modular options and builds and ships most new gearboxes in a day.  

Preventive maintenance and STOBER support 

Follow each OEM maintenance schedule and record loads and repairs. For serviceable units, sample oil to detect contamination and wear. Keep track of vibration and temperature, and inspect the seals, mounts, alignment, and breathers.  

Some sealed STOBER units do not require any oil changes. We also offer failure evaluations, spare parts, repairs, rebuild support, and application guidance for OEMs, with our experienced aftermarket team ready to review oil, bearings, and seals. 

Next steps: Assess your faulty gearbox 

Keep your model manual nearby as inspection limits vary by unit. You can also refer to our gearbox inspection checklist as a field reference:  

• Record the model and serial number, operating history, oil level, symptoms, recent alarms, and any changes in load.  

• Add photos and vibration, temperature, or oil data.  

• Then, contact STOBER engineering with your findings to request an evaluation and quote. 

• Review the report before choosing a repair, rebuild, or replacement gearbox.  
• For washdown equipment, discuss the cLEAN System and any integration needs.