1. Drain and Fill. Changes about 70% of the dirty fluid out. Typically costs between $40-$50. This one is very similar to a standard oil change where they open a drain plug, drain the oil that's in the oil pan and fill up the trans with new oil. Typically the torque converter does not get drained, which is why it typically only replaces about 70% of the fluid. On older vehicles, the entire oil pan must be dropped and a new gasket used to reseal the transmission and a filter is usually replaced.
2. Full Trans flush. Where new transmission fluid is drawn in and the old fluid pushed out. Typically changes about 95% of the dirty fluid out. Typically costs around $150. Typically a machine is hooked up to the transmission cooling line where clean trans fluid is drawn into the transmission as older fluid is expelled into another chambler.
This gets most of the dirty fluid out of the transmission.
