Fault source analysis: Gear oils

Year of publication: 2003

OELCHECK is on the trail of wear. We decipher the message of the oil with our lubricant analyses. With their personal diagnosis, the experts from OELCHECK provide valuable information on irregularities and impending damage. A detailed examination of the engine or the affected machine should then be the consequence.

For a quick and most efficient check-up, OELCHECK has summarized many of the possible causes in a large guide to fault source analysis for engines, gears and hydraulics. You can find the error source analysis for gear oils in this article.


Table of contents

  1. Problem: Remarkably high wear
  2. Problem: High levels of water, dirt or dust
  3. Problem: Overheating of the gear or oil oxidation

Problem: Remarkably high wear

  • Check the magnet in the drain plug for conspicuous particles
  • Check magnet plug (if present)
  • Drain oil through a screen, fine filter or tightly woven cloth, check for particles
  • Check gear under motion for running noises, vibrations, oil pressure, bearing play, leaks, seals
  • How was the sample taken?
  • Do not take samples from the bottom of the oil pan or from the oil sump, but always take an oil sample from the center stream of the drain at operating temperature
  • If the oil sample is not representative, large particles may be missing altogether or disproportionately present.
  • Was there always enough oil in the system, was the gear unit operating at extreme lean angles?
  • Was the correct oil type always used?
  • Are the wear particles from pre-existing damage or from a previous problem?
  • Was the oil changed properly?
  • Check alignment of axles and bearing and transmission clearances.
  • Check differential lock, if present.
  • Is the oil pump running correctly?
  • Extremely long oil change intervals
  • Varying abrasion on wet brakes or drive belts

Problem: High levels of water, dirt or dust

  • Defective seals on shaft passages
  • Damaged or missing air intake filter (breezer)
  • Loose covers or protective caps, damaged cover or housing seals
  • Incorrect oil storage – standing barrels with open or dirty openings
  • Dust ingress during oil refilling due to dirty refill cups
  • Water from cleaning work with the steam cleaner
  • Condensation water due to low operating temperatures or blocked housing ventilation
  • Oil cooler leaking
  • Error when taking the oil sample

Problem: Overheating of the gear or oil oxidation

  • Drain oil pan completely and clean it
  • Oil level too low
  • Crusty dirt deposits on the gear housing
  • Oil cooler does not work or works only partially
  • Wrong oil type, unsuitable oil
  • Overloading of the gear, frequent load changes
  • Bad alignment of the axles
  • Local overheating due to frictional heat caused by wear problems
  • Heat transfer from other components such as brakes
  • Differential lock permanently activated
  • Too much frictional heat due to wet brakes