You will need the following tools:
- 17mm wrench
- 8mm Allen wrench
- Oil filter wrench
- Oil drain pan
Here is the procedure for refilling the transmission oil:
1. Start by raising the car with a jack or by driving it onto ramps.
2. Once the car is raised, locate the transmission oil drain plug. It is located on the bottom of the transmission pan, towards the rear of the car.
3. Place the oil drain pan beneath the drain plug and loosen the plug with the 17mm wrench.
4. Allow the transmission oil to drain completely.
5. Once the oil has drained, replace the drain plug and tighten it with the 17mm wrench.
6. Locate the transmission oil filter. It is located on the side of the transmission pan.
7. Remove the transmission oil filter with the oil filter wrench. Be careful not to spill any oil.
8. Install the new transmission oil filter and tighten it by hand.
9. Place a new transmission oil pan gasket on the transmission pan.
10. Reinstall the transmission pan and tighten the bolts with the 8mm Allen wrench.
11. Locate the transmission oil fill plug. It is located on the top of the transmission pan, towards the front of the car.
12. Remove the fill plug and fill the transmission with new oil. You will need to add about 3 liters of fluid.
13. Replace the fill plug and tighten it with the 17mm wrench.
14. Start the car and let it run for a few minutes.
15. Check the transmission fluid level and add more fluid if necessary.
That is how you refill the transmission oil in a BMW 325i.
