1. Lift the front of the vehicle with a floor jack and slide jack stands under the BMW’s frame rails. Lower the vehicle onto the jack stands.
2. Crawl under the center of the vehicle until you have a clear view of the driver’s side of the transmission.
3. Look on the about one-quarter of the way up the driver’s side of the transmission and about halfway down the length of the transmission to find the check-and-fill plug, which is essentially a hex-head bolt.
4. Position a drain pan under the check-and-fill plug and remove the check-and-fill plug with a ratchet and six-point socket.
5. Insert your finger inside the check-and-fill hole and feel for the fluid inside the transmission. A correctly filled transmission has a fluid level right at the base of the check-and-fill hole.
6. Slide a flexible-neck funnel into the check-and-fill hole and pour new Dexron-III automatic transmission fluid through the funnel and into the transmission if the fluid is low. Continue adding fluid until it drips from the check-and-fill hole.
7. Clean the check-and-fill plug, using a clean, lint-free cloth, then hand-thread it into the check-and-fill hole. Tighten the check-and-fill plug to 37 foot-pounds using a torque wrench and six-point socket.
8. Raise the BMW off the jack stands and remove the stands. Lower it to the ground.
Automatic Transmission With Dipstick
9. Park the BMW 325 on a flat surface. Leave the vehicle idling with the air conditioning turned on until it reaches operating temperature, which is roughly halfway up the temperature gauge.
10. Hold the brake pedal down and shift the gear shifter into each gear. Pause for a few seconds at each gear to allow it to engage. Return the gear shifter to “Park."
11. Remove the transmission dipstick and wipe the fluid off of the end of it with a clean, lint-free cloth. Reinsert the dipstick and remove it again. Lay the dipstick on a flat surface and measure from the base of the dipstick to the top of the fluid level on the dipstick using a ruler.
12. A correctly filled transmissions fluid level is between 1 1/100 and 1 1/2 inches – 26 to 38 mm – from the base of the dipstick.
13. Insert a funnel into the dipstick tube, if the fluid is low, and pour new Dexron III automatic transmission fluid into the dipstick tube in quarter-quart increments, rechecking the fluid level after each quarter quart until it reaches the specified range.
14. Reinsert the dipstick and turn the engine off.
Automatic Transmission Without Dipstick
15. Fill a clean fluid pump with new Dexron-III transmission fluid and connect the pump to an electrical outlet or compressed air source, depending on the type of pump you use.
16. Park the BMW on a flat surface with the engine idling. Allow the engine to idle until the temperature gauge begins to rise. Do not allow the vehicle to reach operating temperature during the checking process, as it will cause an inaccurate reading.
17. Hold the brake pedal down and shift through all of the gears, pausing at each gear for a few seconds to allow it to engage. Return the shifter to “Park.”
18. Lift the front of the vehicle off the ground using a floor jack and slide jack stands under its frame rails. Lower the front of the vehicle onto the jack stands. Raise the rear of the vehicle and slide jack stands under the rear part of the frame rails. Lower the rear of the vehicle onto the stands. Never attempt to check the automatic transmission’s fluid with just the front of the vehicle lifted, as this will give you an inaccurate reading.
19. Find the transmission check-and-fill plug on the base of the transmission. The precise location varies greatly, depending on which transmission your 325 has, but the majority of them are along the side of the transmission pan or the side of the transmission housing. One exception is the A5S310Z transmission, which has its check-and-fill plug on the base of the pan. In this case, the check-and-fill plug is the larger of the two plugs on the pan.
20. Position a drain pan under the check-and-fill plug. Remove the check-and-fill plug with a ratchet and the appropriate attachment. Some transmissions have a hex-head bolt that require a six-point socket, some require a Allen-bit socket and others require no attachment, just the drive of the ratchet.
21. Watch for fluid to flow from the check-and-fill hole. If fluid does not flow from the hole, the transmission fluid level is low.
22. Insert the fluid pump’s tube into the check-and-fill hole and pump fluid into the transmission until it flows from the hole, if the level was low.
23. Clean the check-and-fill plug with a clean, lint-free cloth, then hand-thread it into the check-and-fill hole.
24. Find the transmission identification placard on the transmission oil pan to determine the type of transmission your 325 has, the options are A5S310Z, A5S560Z, A5S440Z, A5S325Z, A4S270R, A4S310R, A5S360R or A5S390R. The torque values for the check-and-fill plug in each transmission are 73 foot-pounds, 73 foot-pounds, 26 foot-pounds, 22 foot-pounds, 18 foot-pounds, 18 foot-pounds, 15 foot-pounds and 15 foot-pounds..
25. Tighten the check-and-fill plug to its specified torque using a torque wrench and the appropriate attachment you used to remove it.
26. Lift the rear of the vehicle off the jack stands and remove the stands. Lower the rear of the BMW to the ground. Repeat this step on the front of the vehicle, then shut the engine off.