I mistakenly removed the "C5" drain plug on my Allison 3000, yesterday, while doing my fist full fluid change at 18,000 mile. It drained a small amount of fluid then stopped. Spoke to our local service manager and he said it was ok to reinstall and fill as normal. I completed the draining using the proper drain plug, R&R'd both filters, added 5 gallons of Transynd; then using AllisonMan's instructions, I flushed the Torque Converter and Heat Exchanger (about 3 gallons) which went exactly as posted. Topped off Transynd, test drove 10 miles (Temp = 189 degrees), added 3 Qts per Shift Controller. DONE! :laugh: Total cost about $350 w filters. Questions: 1) Any possible damage done by removing the "C5" drain plug? 2) Is there a way to test the actual percentage of Transynd obtained after the flush. 3) If I get a high enough percentage, I assume that I could go to the 3 yr change interval? Any thoughts would be appreciated.