1.  Field of the Invention
The present invention relates to changing automatic transmission fluid (AFT) in a motor vehicle.  More specifically, the present invention provides for an apparatus and method for replacing automatic transmission fluid in an automatic transmission in a motor vehicle. 
2.  Description of the Prior Art
Many consumer and industrial devices today use automatic transmissions filled with automatic transmission fluid (ATF) as the working fluid.  To maintain the integrity of an automatic transmission in a motor vehicle, automatic transmission fluid should be periodically removed from the automatic transmission and replenished with fresh automatic transmission fluid; especially since transmission fluid properties deteriorate with mileage of the motor vehicle because of heat and pressure of the motor engine.  As an automatic transmission wears with time, minute particles of metal and the like, as well as carbon and similar substances from various materials in the automatic transmission, mix with the automatic transmission fluid and form deposits. 
Associated components of an automatic transmission include the valve body assembly, the torque converter, external and internal automatic transmission fluid passages and lines and the automatic transmission cooler.  More often in late model vehicles, these associated components are being subjected to severe heating and cooling cycles.  The components are smaller in size, have less surface area, and are packed into tight areas that are spaced from the primary air flow, often very close to vehicle exhaust systems including hot catalytic converters.  In addition, cooling systems are purposely maintained at higher than ever temperatures to improve engine combustion efficiency.  These cooling systems are the primary source of automatic transmission fluid cooling.  As previously indicated, the result of these conditions on today's automatic transmission and its associated components, is the formation of deposits throughout the system. 
These deposits are primarily the result of metallic particulates and oxidized ATF.  They require a chemical cleaner for cleaning purposes because they cannot be removed just by exchanging or transfusing the automatic transmission fluid.  Oxidation is a normal degradation process on petroleum based oils.  However, continuous heating and cooling to the extremes, as seen today, will greatly expedite this oxidation process.  These deposits will form in critical areas such as in the valve body of the transmission where gear shifting is controlled, as well as in automatic transmission fluid lines and in automatic transmission fluid coolers.  Many original equipment manufactures of the motor vehicles now recommend flushing of the automatic transmission fluid lines and coolers to remove the deposit build up.  The deposits are coating lines and coolers, thus restricting fluid flow and proper heat transfer for cooling.  If automobile and truck automatic transmission fluid changes are not made at the designated periods, slippage of the automatic transmission may occur and, eventually, the transmission fails. 
When automatic transmission fluid is drained at recommended periods from a transmission case, the used transmission fluid will typically be found to be dark, indicating contaminants in the transmission fluid.  Furthermore, the transmission fluid present in the transmission case is only a small portion of the transmission fluid actually in the automatic transmission, as a large quantity of the transmission fluid remains in the torque converter, the transmission fluid cooler , and in other control circuits and components of the automatic transmission.  It has been estimated that 50% or more of the transmission fluid is not, removed by draining only the transmission case.  Thus, after the traditional method of changing automatic transmission fluid, a significant portion of the transmission fluid still contains contaminants because after the traditional transmission fluid change, the quantity of contaminants in an automatic transmission and its associated components will accumulate with successive fluid changes, especially since the transmission will be forced to operate with a mixture of used or old transmission fluid and new or fresh transmission fluid.  Such operation will reduce the efficiency and life of the automotive transmission. 
These problems have been recognized by the prior art.  U.S. Pat.  No.  5,291,968 to Brown teaches a drain pan under a transmission, and the collecting of transmission fluid in the drain pan for disposal.  Brown then uses an external pump to force new transmission fluid from a reservoir into an outlet of the transmission.  The engine is subsequently used to pump the remainder of the used fluid out as the fresh fluid is pumped in.  Brown notes that simply removing the transmission pan allows only about three quarts of fluid to be drained of a transmission fluid capacity of twelve quarts. 
U.S. Pat.  No.  5,318,080 to Viken teaches a fluid receiver for used transmission fluid, a source of supply of fresh transmission fluid, and a pneumatic cushion for coordinating the introduction of fresh fluid into a transmission with the draining of used transmission fluid therefrom.  More particularly, the pneumatic cushion is provided intermediate individual receptacles for receiving used transmission fluid and adding new transmission fluid while pressure within the receptacles is maintained at a predetermined level commensurate with the normal operating pressure of the fluid in a given transmission. 
U.S. Pat.  No.  5,361,870 to Courcy discloses a transmission fluid exchange apparatus comprising a tank structure arranged to include a piston within the tank structure to divide the tank into a first and second chamber.  A piston rod is fixedly and coaxially mounted to the piston and extends through the second chamber and into the exterior of the tank.  The first chamber is arranged to receive used transmission fluid while simultaneously fresh transmission fluid is directed from the second chamber into an associated transmission line.  The piston rod has rod graduations along an exterior surface thereof for indicating various incremental fluid directed from the tank. 
U.S. Pat.  No.  5,427,202 to Behring et al.  discloses an apparatus to flush transmission fluid from a vehicle.  The vehicle has a transmission fluid cooler with a first line extending from a transmission to the cooler to carry transmission fluid to the cooler and a second line from the cooler to the transmission to carry cooled transmission fluid back to the transmission.  The apparatus comprises of a storage tank and a means to connect one of the lines to the storage tank to direct the old or used automatic transmission fluid flowing through the line into the storage tank.  A supply tank is provided with replacement automatic transmission fluid therein.  A filling apparatus is connected to the supply tank and into the automatic transmission dipstick tube to continuously supply fresh replacement automatic transmission fluid to the automatic transmission simultaneously with the used automatic transmission flowing to the storage tank. 
U.S. Pat.  No.  5,447,184 to Betancourt teaches a flushing system that thoroughly flushes out a transmission in a single sitting, purging it while running, and flushing through a volume of oil equal to 3 to 5 times the fluid capacity of the transmission to ensure the complete replacement of all fluid in all ports and passageways.  Betancourt indicates that an important feature of his system enables the operator to ascertain the normal flow direction of the fluid in the transmission cooling system under action of the vehicle's pump.  Once the operator determines the normal flow direction of the fluid, if the lines of the purging system turn out to be reversed, they can be switched with a valve without having to remove and switch the hose connections between the transmission and the flushing system.  Betancourt also discloses a means to monitor and control flow rates into and out of the transmission so that the fluid level remains stable. 
U.S. Pat.  No.  5,472,064 to Viken discloses a total fluid exchange system for automatic transmissions.  Regulated compressed air provides pressure to deliver fresh fluid to the automatic transmission.  Viken provides for various valves, gates, pressure, and other indicator or control elements to maintain proper directed fluid flow.  A pair of position valves allows for either straight through flow or reversal flow between two lines which carry used and fresh fluid to and from the opened cooling circuit.  Viken also provides for an electronic system with a microprocessor and a control panel for entering simple on/off commands and for indicating the status of key function.  A printer is provided to produce a written record of the service by specifying pressure, rate of flow before and after clarity of fluid, and the total number of quarts of fresh fluid used.  The microprocessor is taught as being able to control all system functions either automatically or semi-automatically. 
U.S. Pat.  No.  5,522,474 to Burman discloses an apparatus for removing automatic transmission fluid from an automatic transmission.  A cylindrical reservoir is provided.  The reservoir has an inlet fitting at one end and an outlet fitting at the other end.  A pair of flexible lines is respectively connected to the inlet fitting and the outlet fitting.  The cylindrical reservoir has a floating piston that can freely move therein. 
The instant invention attempts to overcome deficiencies of the foregoing prior art by providing for a simple, cost effective apparatus and method that completely flushes and cleans the entire transmission and replaces the transmission fluid.  The apparatus and method of the present invention overcome disadvantages of the prior art and satisfy the need for an improved concept for cleaning a transmission and its associated components and for changing automatic transmission fluid.