To check the transmission oil level in the manual transmission of the Audi A4 3rd generation, put the car on flat horizontal ground. Then unscrew the oil filler plug (located on the crankcase of the box). Using a suitable object (for example, a wire) determines the oil level. For GYH-indexed boxes, the oil should be at the lowest edge of the hole. For other box models, the normal level is 2-3 mm below the edge. If necessary, add oil through the hole with a syringe. Tighten the filler plug to a torque of 40 Nm.