Technical guides
Practical guides from our parts desk for technicians and owner-operators.
How to measure brake pushrod stroke
A step-by-step method for measuring stroke on S-cam brakes, the limits inspectors use, and what to replace when the numbers are high.
Read the guideSetting filter service intervals
How fleets balance the engine maker's schedule with fuel quality, duty cycle, and oil analysis results.
Read the guideAir dryer cartridge service
Signs of a saturated cartridge, how to replace it, and what to check in the rest of the air system.
Read the guideWhich guide to open first
Start with the pushrod stroke guide when a tractor or trailer fails an air-brake inspection, pulls under braking, or shows uneven lining wear. That guide walks through cold measurement at full application, the clamp-chamber limits published in 49 CFR 393.47, and the parts that usually fix a high reading: slack adjusters, chambers, shoes, and related wheel-end hardware.
Open the filter intervals guide when you are rewriting a preventive-maintenance sheet for a Cummins, Detroit, PACCAR, Volvo, or Mack highway engine. It explains how fuel quality, idle hours, oil analysis, and restriction indicators change the calendar the engine maker publishes, and it points to lube, fuel, fuel/water, and coolant filters stocked in this catalog.
Use the air dryer cartridge guide when tanks show water, a purge sounds wrong, or winter freeze-ups start at valves. Cartridge service is a short job when the housing, purge valve, and heater are sound, but it fails early if the compressor carries oil. The guide separates cartridge-only work from full dryer assembly replacement and links the Bendix AD-IS and AD-9 cartridges we list.
These pages are shop notes, not a substitute for OEM service information or the inspection criteria used in your state. When a stamp on the old part does not match a catalog row, email a photo to the parts desk before you order.
How we write guides
Each guide covers one job that comes up often at the parts counter. We explain what the part does, how to recognize a problem, how to check it, and what to buy. We link to the parts that match the job, but we do not hide advice behind a sales pitch. If a repair does not need a new part, we say so.
Guides are general information. Your truck's service information, applicable inspection standards, and your own training come first. Part numbers and fitment on this site are a guide and should be compared with the old part before you order.
Have a topic you would like to see? Write to support@aonetruckauto.com and tell us what you were trying to fix.