6.6L Duramax F/R Crankshaft Seal Service Kit Master kit for servicing the front and rear crankshaft seals on 2001-2016 6.6L Duramax diesel engines. Includes CTA 3878, 3879, 4042, 4043. Installers properly fit the inner and outer seal bodies while the removers use controlled force and jaws to prevent seal and engine damage. Services GM, Isuzu, and GMT800 HD trucks needing front and rear crankshaft seal removal and installation. Compare 3878, 3879, 4042 and 4043 to GM factory tools J-44642, J-44645, J-44641 and J-44644 4044