New fluid is clean bright red in color.
The best flush will include dropping the pan, cleaning the pan, changing the filter, and include a pre-flush treatment and a post-flush treatment. Lower flushes only include draining oil and refilling oil or just a filter change and replace the fluid lost.
Why should I change it?
Over time the filter can clog up which causes a lower volume of oil flow causing slow shifting or slippage. Also, transmission fluid is petroleum based oil and with age it breaks down and loses its friction characteristics. When this happens, it turns dark brownish-red in color and has a slightly burnt smell to it
A transmission flush is a lot like an oil change but for your transmission. Under normal driving conditions heat and oxidization will deteriorate transmission fluid and the level of contaminants and debris increase. If the transmission is put under greater stresses by towing, operating under a load, hot climates or by stop-and-go city driving, the rate of deterioration increases. A flush will help to decrease glazing and wear on your transmission components by removing particles and debris from the transmission before causing hard part failure.