will 178.704 put my truck out of service
No. Across our 13 million inspection records, 178.704 citations have never resulted in an out-of-service order—the OOS rate is 0.0%. This code is not OOS-eligible by rule. Compare that to the national average FMCSR OOS rate of 31.4%, and you'll see this is a documented violation without immediate roadside enforcement power. You'll receive a citation, but your truck stays in service.