Volvo's Aisin-Warner-based automatics are extremely durable, but their lifespan depends on clean oil. Old, burnt oil wears clutch plates and clogs the valve body.

Data / BW-55 AW-55 / AW-70 AW-71 Ratio 1. / 2.45 : 1 / 2.45 : 1 Ratio 4. (OD) / - / 0.69 : 1 Oil volume / approx. 6.5 – 7.0 liters / approx. 7.5 liters Turbine portion / approx. 2.5 liters / approx. 2.5 liters Oil grade / ATF Type G (F) / Dexron II/III (from 1984-) Note: Gearboxes manufactured before 1984 often require oil conforming to Ford M2C33-F or G standards. Always check your owner's manual or dipstick for the correct grade for your car.

Automatic transmission oil must not be measured with the engine off. Drive the car until warm (approximately 15–20 km). Park on level ground and let the engine idle. Move the selector lever through all positions (P-R-N-D-2-1) and leave it in P position. Lift the dipstick, wipe it with a lint-free cloth and reinsert. The level should be between the HOT zone marks. Add if necessary through the filler tube.

Simply opening the drain plug only changes about a third of the oil. By circulation you can also change the dirty oil in the turbine and cooler. Work steps: Drain: Open the oil pan drain plug and drain the oil into a measuring container. Replace the copper washer and close the plug. Fill: Add new oil through the filler tube in exactly the same amount as came out. Circulation: Disconnect the oil cooler return line (usually the lower line at the radiator end). Direct the line into a clear measuring container. Pumping: Start the engine at idle. Let it pump out 1 liter of oil and turn off the engine. Addition: Add 1 liter of new oil through the filler tube. Repeat: Repeat steps 4 and 5 until the oil coming from the return line is bright red and clean. Finishing: Reconnect the return line, check the level (first using the cold scale) and take a test drive.

It is normal if shifts feel somewhat vague or delayed during the first few kilometers. The system may have air in it, which will escape during driving. If problems persist after 5–10 km, recheck the oil level when hot. Warning: If the oil coming out is black and smells strongly burned, the clutch plates may be at the end. In that case, oil change alone may not fix the mechanical fault.