New lightweight aluminum overflow canisters for Powerglide, TH400 and Ford C4 transmissions safely contain high-rpm fluid blow-by Transmission fluid should always stay in the transmission; while it seems like a simple principle, it can be difficult to achieve. At high rpm, it is not uncommon for fluid to escape through the transmission vent - spreading oil on the undercarriage of your racecar. To eliminate the resulting safety concerns and messy clean-up, TCI® offers three new PRO-X™ Overflow Canisters, which weigh less than two pounds, hold approximately one quart of fluid and attach to the transmission pan in three easy steps.