The increasing focus on automotive automatic transmission contamination levels needs to result in both dramatic manufacturing system changes and transmission filtration needs. This paper focuses on defining and quantifying automatic transmission contaminant levels and the filtration needed to remove this contaminant.Specific data are presented which quantify the particle count and gravimetric level of transmissions oil samples. The debris found from numerous used filter analyses is also presented. Representative transmission valve contaminant sensitivity data is then shown which highlights the deleterious effect contaminant has on transmission valve operation.This paper concludes with the particle removal efficiency of common transmission sump filters being shown to be unable to remove many of the most damaging particles which result in transmission valve sticking, wear, and general shift quality degradation. Recommendations for correcting this situation are presented.