This is a strong and solid methodology to define and/or verify how the dimensional schema of the parts and their statistical variation affect the assembly variation.This study has been done to fix an issue in the assembly line of a Cummins' customer. This is a problem that occurs during the assembly of the Linear Belt Tensioner.The voice of customer says “Many times it is too hard to assemble the Belt Tensioner!”The paper shows the analysis performed at Cummins Brazil. The analysis process utilized the Dimensional Variation Analysis methodology, statistical software - Minitab, Pro/Engineer and CETOL 6 Sigma to verify the length of the FEAD (Front Engine Drive Accessories) belt path., The results were compared with the variation of the Belt length.The voice of customer was proved by the three-dimensional DVA analysis. The design shows up to 16% of the FEADs could have problems during the assembly. The improvement in the assembly line and in the design has been defined based on these results and methodology.