When I first installed the MAG-HYTEC trany pan, I removed the old pan, replaced the filter with a new one, installed new pan. Filled trany with new ATF (AMSOIL) till at full line. Removed the line at the transmission, that is the return line from the cooler. Slipped a peice of hose over it, that was long enough to reach a 5 gal pale. Then just start the truck, and watch the flow, when you pump out about 3-4 quarts, stop and top off the transmission, then repeat. Keep doing this till you can see the new fluid coming out, it is bright red, and not dark red like the old fluid. Then just re-attach the line, and top back off.