Popping
Just to throw another idea out at you. Our rig is on a F-53 chassis but our "popping" noise started when we hit a hard bump on a SoCal highway. Long story short, found out that a weld on the right front brace area directly under the passenger's foot area broke. Many people opined that it was bushings, loose nuts, etc. Rig has 10000 miles on it by the way. Rewelded and the popping noise is gone.
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