The Audi A4 is the subject of consumers' reports of gearbox problems which hamper the steering and transmission of the vehicle; everything from the electronic control unit (ECU) on the transmission failing to the automatic gearbox jumping out of gear, harsh shifting, delayed shifting or loss of mobility completely.
ATF Pump Bushing
A technical service bulletin (TSB) published on the Audi A4 by the manufacturer concerns the failure of a bushing on the automatic transmission fluid (ATF) pump. This bushing failure causes the pump to lose pressure and eventually causes the transmission to fail. The Audi will begin to hesitate between shifting gears or upon acceleration. The bushing is part of the valve body and cannot be replaced without replacing the entire ATF pump... but an ATF pump of better quality must replace it in order to prevent the bushing from failing again.
Electronic Control Unit Failure
ECU failure is a common Audi A4 gearbox problem. The ECU controls the movement of the transmission when the gears are being selected. Once the ECU begins to fail, a warning light on the dash of the Audi will illuminate, notifying the operator that there is a gearbox problem. The warning light also notifies the computer on the Audi, and places the transmission into a fail-safe mode to prevent damage to the transmission and gearbox. The Audi will lose power, reverse gear can be lost or the Audi will not move when shifting into drive. No one cites a specific reason for the ECU failing, and there has been no recall on the Audi.
Another common problem with the Audi A4 gearbox is when the transmission begins to slip. The gearbox slips when a driver is accelerating the Audi. The gearbox should hold each gear in place at different speeds, but once the gearbox begins to slip there will be a jerking or hesitation during acceleration. Reports state that this gearbox problem can be the result of several issues including low transmission fluid, gear lever adjustment or worn internal gears. The Audi A4 needs to go to a qualified technician as soon as these symptoms develop or major damage may affect the gearbox.