Short answer: For one-side tracking or weak travel: ① compare both tracks at full speed, ② drain the final drive oil (milky = water, glitter = gear damage), ③ check the travel motor case drain flow, ④ test pilot pressure to that joystick. Clean oil + normal noise usually means the problem is upstream (pump, joystick, pilot lines) — do not order a motor yet.
Symptom → likely cause
| Symptom | Likely cause |
|---|
| One side slower than the other | That side motor/relief, or uneven track tension |
| Strong on flat, stalls on slope | Planetary internal leakage under load |
| Oil weeping at shaft seal | Seal aged — replace early, protects the gears |
| Milky final drive oil | Water ingress via seal or breather |
| Clicking once per revolution | Chipped planet gear — stop, metal spreads |
The 4-step check
- Track comparison: full-speed forward on both sticks — 10%+ difference points to the slower side.
- Oil check: open the final drive plug on a cold machine; milky = water, glitter = gear damage, low = leak.
- Case drain: excessive drain flow from the travel motor confirms internal leakage.
- Pilot pressure: weak pilot to one joystick can fake a motor failure — cross-test the other function on the same circuit.
Maintenance that prevents 90% of failures
- Change final drive oil every 500–1,000 hours — the most neglected oil on the machine.
- Never point a high-pressure washer at the shaft seal.
- Replace the breather whenever you service the oil.
Travel motors, planetary parts, shaft seals and final drive oil for mainstream models — search in All Parts.
Frequently asked questions
Can a final drive be repaired instead of replaced?
Yes — planetary gears, bearings and seals are replaceable when the housing is intact.
How often to change final drive oil?
Every 500–1,000 hours; sooner in water, mud or abrasive conditions.
One side slow but oil is clean — motor bad?
Not necessarily: cross-test pilot pressure and track tension first; clean oil and normal noise often mean an upstream cause.
Need a travel motor or parts?
Send the model and part number — same-day quote, factory direct.