You never run pure ATF in the engine, it is not a real good lubricant, it's more of a hydraulic fluid, add a quart maybe and let it run for a few minutes, you can also add kero and do the same thing but dont drive it or over rev it, just let it idle for 10-15 minutes, both kero and atf are very high detergent. Then do the oil and filter change with cheap oil and keep an eye on it. The kero or atf will soak into the sludge and even after draining it it will over time start to break it down which will start clogging the oil filter at which point the bypass kicks in and you are running unfiltered oil. You need to check the dipstick every 5 or 6 hours of driving and when you can no longer read the marks or words on it change the filter and add a quart of oil.
Running synthetic full or half strength will clean it a bit more gradually and with no danger to the bearings and stuff. Then you also need to keep an eye on the dipstick and change the filter as needed.. don't be fooled with the premixed semi-synthetic, do the math, just pick up 3 quarts of organic motor oil and 3 quarts of synthetic, then you will have a 50/50 mix.
I've used seafoam in the gas tank, cleaning the carbon out and thats about it, Oh, did put in the oldsmobiles transaxle to try and clean that up but it did not work, ended up replacing the transaxle a month later but it was on it's way out anyway..
