What 393.51(d) means in plain language
Your steering wheel has too much play—the amount of rotation you can make at the wheel before the front tires actually respond. Every steering system has some built-in free play by design, but there are federal limits based on your truck's specific steering configuration.
When an inspector measures your steering wheel and finds it exceeds those limits, they cite 393.51(d). This isn't about your truck being unsafe necessarily; it's about being out of specification. A worn or improperly adjusted steering column, gearbox, or linkage can creep past the allowable threshold over time, often without you noticing in normal driving.
What our enforcement data actually shows
Across 13 million roadside inspections in our database, 393.51(d) has been cited only 2 times all-time, with zero citations in the last 12 months and zero in the last 90 days. This code ranks #2651 of 3,036 FMCSR codes by citation frequency—it is exceptionally rare.
Neither of the 2 all-time citations resulted in an out-of-service order, giving this code a 0.0% OOS rate. By comparison, the all-FMCSR average OOS rate is 31.4%, meaning inspectors almost never use this violation as grounds for immediate roadside removal. This reflects both its rarity and the fact that inspectors typically allow time for repair before impounding the vehicle.
Who gets cited most
With only 2 citations in our entire 13 million-record database, carrier and state patterns are not meaningful to report. The two violations occurred at carriers with 1 citation each: Transportadora Norte de Chihuahua S A de C V and Jorge Humberto Maldonado Gonzalez. This data volume is too small to indicate any trend or carrier-specific risk.
How severe is this compared to similar codes
Vehicle maintenance violations span a wide range of enforcement intensity. Inoperable required lamps (393.9(a)) has generated 660,737 citations with a 15.4% OOS rate—making it far more common but somewhat less likely to result in immediate removal. Slack adjuster defects (393.47E) have generated 180,363 citations with a 0.0% OOS rate, similar in enforcement pattern to 393.51(d). General inspection and maintenance violations (396.3(a)(1)) are even more frequent at 236,919 citations but carry a much higher 45.3% OOS rate, indicating inspectors view them as more immediately hazardous.
How to avoid it
Steering system wear is often gradual and easily overlooked. Here are concrete steps you can take before and during your pre-trip:
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Check your steering wheel movement weekly. Grasp the wheel at 3 and 9 o'clock while the truck is parked and the engine off. Gently try to rotate it left and right. If you feel more than a quarter-turn of movement before the wheels respond (or before you feel resistance), that's a sign of excessive play. Note the amount and report it to your fleet maintenance team immediately.
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Inspect the steering column for damage or looseness. Look where the column enters the dashboard and where it connects to the gearbox. Tighten any visible bolts if you are authorized to do so, or log the issue for your mechanic. Loose fasteners are a common cause of play buildup.
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Have steering linkage checked during your next scheduled service. This includes the tie rods, steering arms, and intermediate shaft. These components wear and can allow play to accumulate. A mechanic can measure free play using a dial indicator and compare it to your truck's specification plate.
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Review your truck's steering specification. Different steering systems (manual, power, or integral) have different allowable free play limits. Ask your maintenance department for the spec sheet for your truck's year, make, and model, and keep it in your cab so you know what "normal" is.
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Document any steering feel changes during normal operation. If steering becomes less responsive, requires more input to turn, or feels "loose" compared to your previous experience with a similar truck, report it to dispatch or your fleet manager before your next inspection.
Because this citation is so rare in the enforcement data, most drivers never encounter it. That rarity suggests that when it does appear, it usually reflects a specific maintenance gap rather than a widespread issue. Catching it during your pre-trip and addressing it promptly will keep you compliant and—more importantly—ensure your steering system is performing as intended.