The Honda Odyssey transmission fluid changes color over time due to worn clutch material contaminating the fluid. It is not open to the atmosphere and is not affected by the engine. Any contamination in the transmission is strictly due to internal wear, which is normal. The Odyssey does not have a traditional filter or oil pan on the transmission. It has a large magnetic drain plug, which attracts all metal shavings that must be cleaned before flushing.
Drive the vehicle to a reputable service facility. Instruct the service writer to drain the transmission, and remove and clean all the metal particles off the magnetic drain plug. When this is clean, refill the transmission.
Instruct the service writer to perform a power flush on the transmission. The reasoning behind this is that it does little good to perform a power flush as long as the magnetic plug is covered with metallic chips. The transmission only gets a flush when the fluid turns from red to brown, which takes a long time. Draining and filling the transmission with fluid does no good, since the majority of fluid is in the torque converter and pump. As soon as the vehicle starts up, the fluid will be dark again. Flushing the transmission involves removing the transmission lines from the radiator and connecting them to a large power flushing machine. The mechanic starts the engine, and the machine forces new fluid into the transmission and pulls the contaminated fluid out until the fluid flows red. This usually requires the machine to dispense about 13 to 18 quarts of new transmission fluid.
Request the service writer to add a clutch-modifier fluid to the transmission fluid after the flush is complete. This adheres to the clutch discs and creates a rougher surface for better clutch engagement. Now the transmission will shift better and faster. The biggest benefit is that it extends the life of the transmission by at least 40 percent.
