So I installed a used transmission and filled it with Royal Purple ATF Max. Its a 2001 trans. Everything sounds good in the trans until I drive it about 30 miles or so. After the transmission is warmed up it rattles in every gear. Also, it has a fairly loud vibration at ~5000 rpm whether or not it is warmed. Other than that, it's good. Shifts good and everything. It's just noisy after it's warmed up. Could it be that the fluid is just too thin after it gets warmed up? Should I switch to syncromesh? It still doesn't explain the loud vibration at 5000 rpm. What do you guys think?