Whoa. No don't use shock proof in the primary. It is loaded with moly. As far as the primary goes a good diesel hdeo like rotella t-5 semi synth 15w-40 is perfect. It's loaded with detergents and zinc to keep clutch plates clean. Shock proof is amazing stuff in the tranny. I use it in mine. I use red line primary oil in the primary although after much research I am switching to a cheap diesel oil. The key is keeping the clutch plates clean for trouble free life. Amsoil 20w50 will work great too,just very costly. Save it for the motor.yes you can, but i would reccomend redline heavy shock 85/140 or belray gearsaver, same visc.