Complaints such as bucking, starting weaknesses, too late upshifting, plucking when starting, vibrations and similar shifting problems of the automatic transmission are known to many employees of a car workshop. The customers complain about this malfunction of the gearbox and want a smooth shifting of the automatic transmission.
This is not always the case because metallic abrasion, residue and deposits that can never be avoided are deposited in the automatic transmission and affect the function of the sensitive control valves, clogging or hindering the flow of oil in the transmission. The metallic abrasion stresses the whole system and affects the lubrication, which in turn can lead to an increased abrasion of the aluminum components. All of this can cause shifting problems and significantly reduce the life of the automatic transmission.
Only by a "complete automatic transmission oil change" deposits in the system can be removed. However, this is usually very labor-intensive and cost-intensive. For some transmission types, it is not possible by design, for example, if the torque converter has no drain plug to perform a conventional replacement of the oil in a conventional manner.
If the transmission oil is simply drained, much dirt remains in the torque converter. These residues return to the oil circuit and this can cause problems again.