Abstract: A filter is disposed in the interior cavity of each of the axle spindle sections of a non-drive axle for a heavy duty tractor-trailer, which utilizes internally vented wheel end assemblies. Each filter provides for sufficient air flow from the wheel end assembly cavity into the axle cavity to enable internal venting of any expanding gas from the wheel end assembly cavity into the axle cavity, thereby preventing excessive pressure build-up in the wheel end assembly and possible reduction of the life expectancy of the wheel end assembly main seal. Depending on the filter embodiment employed, the filter prevents or at least lessens the likelihood of migration of contaminates such as oxide scale from the axle cavity into the wheel end assembly cavity, thereby preventing or lessening the likelihood that such contaminates will cause premature wear of the wheel end assembly bearings or main seal.