Michigan State Brakes Certification Practice Exam

The presence of gear lube inside both rear brake drums on a rear wheel drive vehicle most commonly indicates that there is an issue with the axle seals, leading to excessive fluid leakage. In this case, the correct answer directly relates to how axle issues manifest in the brake system.

When the seals or bearings in the axle housing fail, gear lube can seep into the brakes, contaminating them. This condition can lead to brake performance issues, such as reduced stopping power or uneven braking force due to the lubricant interfering with the friction materials on the brake shoes.

While the other options may also suggest potential issues with the braking system, they do not directly connect to the observed symptom of gear lube inside the brake drums. A leaking differential would typically result in oil leaks in different areas, plugged axles may not necessarily lead to lube in the drums as it would more commonly cause issue with the differential's function itself, and worn brake shoes would not be associated with the presence of gear lube specifically.