Quote:
Originally Posted by Fat Charlie
The 5.9 "Heavy Duty" was simply a 5.9 V8 without as much in the way of emissions controls. The HD rating was just an emissions thing, not a performance thing.
|
The Heavy Duty designation actually means having a GVWR over 8500 lbs (actually classed as a Medium duty truck) which at the time (maybe still) had different emission standards.