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One shoe wearing much faster than its mate on the same wheel end most commonly points to a mechanical problem that prevents equal shoe movement. If a shoe roller, anchor pin, or related hardware is seized or damaged, one shoe may not apply (or may release slowly), forcing the other shoe to do most of the braking work and wear faster. A slack adjuster problem typically changes overall clearance and affects braking on that wheel end more uniformly, rather than causing one shoe to do nearly all the work when pushrod stroke is already within specification. Worn S-cam bushings can cause poor brake feel and irregular contact, but the most direct cause of one shoe being held back is binding at the rollers/anchors. Lining contamination from a seal leak would usually affect both shoes on that wheel end and would be evident as wet/greasy linings.

Excessive side-to-side movement at the pitman arm where it exits the steering gear housing (with the mounting bolts and pitman arm nut confirmed tight) points to internal steering gear wear or excessive lash. Wear in the sector shaft bushings/bearings or gear mesh allows the sector shaft to shift and creates steering wheel free play, and the looseness can produce a knock when steering load reverses during tight turns. A loose pitman arm nut or loose steering gear mounting can also cause play and noise, but these were specifically ruled out by the inspection. A worn idler arm typically causes linkage looseness on the opposite side of the center link and does not create lateral movement at the steering gear output shaft itself.

In an HEUI system, the injector is oil-actuated: high-pressure engine oil provides the force that hydraulically intensifies and controls injection inside the injector. The high-pressure oil pump supplies this actuation pressure, while the ECM commands injection timing/amount by energizing a solenoid or control valve on the injector. A fuel injection pump is used to pressurize fuel in systems where fuel pressure is generated outside the injector (such as pump-and-line or common-rail arrangements), not to provide HEUI actuation oil pressure. A mechanical camshaft physically actuates injectors in mechanically actuated unit injector designs, and diesel fuel lines only deliver fuel and do not create the hydraulic actuation pressure.