The longitudinally installed BMW E46 drivetrain came with a choice of three styles of transmission:
- Manual 6-speed transmission with manual clutch.
- Sequential manual 6-speed gearbox (SMG) with automatic computer controlled hydraulically operated clutch. SMG models are equipped with paddle-shift levers on the steering wheel.
- Automatic 6-speed Steptronic transmission with choice of Normal, Sport or Manual mode. When Manual mode is engaged, the driver can upshift or downshift through gear ranges by flipping the shift lever forward or backward.
The manual and SMG transmissions are filled with manual transmission fluid, while the automatic transmission is normally filled with "lifetime" fluid. However, BMW does not define what the lifetime is. Therefore, it is a good idea to replace your fluid every 60,000 miles. If you are unsure of the last service, replace the fluid as soon as possible. Doing so will extend the life of your transmission. There are many options for replacement fluid. Choose the best you can afford and be sure it meets BMW's current specifications for your vehicle. To determine the type of fluid that belongs in your transmission, check your owner's manual, or give our parts specialists a call.
ATF is used to fill the automatic transmission but also fills the torque converter, an integral component for transferring engine power to the transmission. The torque converter is a compact turbine, which is bolted to the end of the engine crankshaft. As it spins at engine speed, an internal set of rotors uses the ATF inside the torque converter to transfer the spin to the transmission input shaft. The transmission then transfers the torque to the driveshaft using clutches and planetary gears.
You have two main options when replacing ATF. You can drain and fill the fluid. Or you can drain the fluid and replace the fluid strainer by dropping the transmission fluid pan. In either case the old ATF inside the torque converter remains and mixes with the new fluid. Don't expect to get all the old fluid out, unless you have access to an ATF flushing machine.
For the first ATF service at approximately 60,000 miles, I usually drain and fill only; on the next one at 120,000 miles I replace the strainer. Replacing the strainer allows you to clean the transmission fluid pan of dirt and debris. E46 models utilize a plastic oil pan with a built in strainer. To service the strainer, you will have to replace the oil pan. The transmission holds about 10 liters of fluid.
In this tech article, I will go over how to replace the strainer and drain and fill your transmission fluid.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.
Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
Drive the vehicle for about three miles to warm the transmission fluid.
Jack up all four corners of your vehicle and support it safely. The vehicle needs to be level when checking and replacing fluid.
Place drain pan under transmission and remove 6mm Allen fluid drain plug (green arrow).
If you are only draining and filling the fluid, skip the next step. You will not have to remove the transmission oil pan.
Once fluid is completely drained, remove transmission pan mounting bolts; there are 22 T27 Torx bolts (green arrow points to dotted area of bolts). Before loosening these bolts, clean all dirt and debris from bolt heads. They strip out easily and are tough to get out once damaged. Then remove transmission pan from transmission. Pull old gasket off transmission and discard.
Depending on the model of your transmission, you could have two strainer/filter styles. One that has bolts holding it in and one that pushes into transmission.
To remove bolted-in strainer, remove two bolts, then pull strainer down, be sure strainer O-ring comes out with strainer. If not, remove O-ring from transmission.
To remove pushed in strainer, pull strainer/filter down, be sure strainer O-ring comes out with strainer/filter. If not, remove O-ring from transmission. Install new strainer/filter in reverse order of removal. Then install transmission fluid pan and tighten fasteners.
|Continue here if only performing a simple drain and fill: Measure the amount of fluid drained from the transmission.|
Remove 6mm Allen fill plug; green arrows point to fill plug location. Fill transmission with same amount of fluid that was drained. Start engine, then apply parking brake, hold your foot on brake pedal and shift transmission through all gears. This will circulate transmission fluid. Place transmission selector in Park, then remove fluid fill plug. Monitor transmission as it reaches a temperature of 100 degrees F. You can check this with an infrared temperature gauge. If a small stream of fluid runs out of fill plug, fluid level is correct. If no fluid runs out, add oil until it starts to run out. Reinstall fill plug and tighten. Once complete, I suggest driving car, allow to cool and recheck fluid level.
Now here's the tip, once you have filled the transmission with the same amount of fluid drained the level should be close to what it was. Start engine, move gear selector as noted above. With the transmission fluid still cold and fluid fill plug removed, monitor the temperature and fluid flow at fill plug. When the fluid warms up it will expand and should run out of fill plug, if it does not, add fluid until it starts to run out. Install fill plug and repeat once vehicle is cool.