For best results over time. Flush the fluid three times in a period of 1500 miles. Use chip atf the first time. Then again after driving 500 miles. Then use a good atf such as Valvoline at 1500 miles. Depending on your driving, change the atf every 20-30K miles as soon as you see it loosing transparency. Just once this time with the good stuff. The reason for this method is that new atf will loosen old dirt that is stuck to the surfaces in the gear box. That loose dirt may ruin the transmission in a short time. To use 32 qt at once of oil will not prevent the problem. Only three flushes will really clean the system.