on my 2000 Harley F150 (4R70W) the truck had 100K on the Royal Purple/Mobile 1 mix and had developed a slight shudder when cold, so I went ahead, got a pail of shaeffers and had a flush done Monday. Sunday afternoon I installed an LPW deep pan and poured in 8 quarts of Valvoline High Mileage ATF to top it off after pan install, then monday AM had the system flushed/filled. I captured some of the royal purple/M1 oil during the pan replacment to send to Blackstone and I'll post up the analysis. The oil was DARK, but did not smell burnt.... I also replaced the rear end fluid w/ Royal Purple 75w140 Sunday Afternoon, so my truck is happy now for the time being.