[Unspec]

Edit 2/23/2024: Updated instructions slightly to reflect ZF's instructions of not letting wheels spin. I had forgotten to update that step of the instructions when shifting into the various gears, my apologies. Also, if you intend on doing the Sonnax Zip Kit later down the road, now is a good time to take note of the separator plate code. See attached pictures for OE Valve Body Code location.

Repeat after me: I will not undo the drain plug until I loosen the fill plug. I will not undo the drain bolt until I loosen the fill bolt

Now that I got that out of the way, onto the guide!

Necessary tools:

• 8mm long allen key (Husky long arm allen key is what I used) OR (ideally) stubby hex bit set
• T-40 bit
• Some kind of fluid transfer device. Power fill tool highly suggested.
• 8mm hex socket
• 10mm hex bit/allen key for drain plug
• Small torque wrench. Ideally one that is accurate in the lower ranges, as you will need to torque the pan bolts to 10nm.
• 4 jack stands. You can replace 2 stands with ramps if you're RWD
• Drain pan
• Chemical resistant gloves, ATF is really bad for your skin and smells like literal BO.
• 8mm and 10mm 12 point box wrench

Nice to have tools:

• Level. You want the pan to be level enough where there's no noticeable tilt in any direction. Doesn't need to be absolutely perfect
• A second pair of hands if not using a power fill tool
• ISTA+ with ENET cable. If not, you need some way of reading transmission oil temperature.
• 8mm and 10mm ratcheting 12 point box wrench

Pan and filter kit, includes replacement fill plug and pan bolts

ATF fluid

People have reported success with aftermarket ATF, but I personally recommend OEM as this isn't a frequent service and I'd rather not risk my transmission.

Note: All images have a blue arrow pointing towards the front of the car, to help you orient yourselves.

1. Remove underbody tray that covers transmission, 2 bolts are covered by the front underbody tray.
2. Remove exhaust support and underbody tray anchor panel thing. You don't have to remove the underbody tray anchor panel thing, but it gets kinda messy if you don't so I'd just do it.
   
   Underbody tray anchor panel thing is held on by 2 10mm nuts
   
   
   
   Exhaust support nuts, use 8mm box wrench. When reinstalling, torque to 21nm. First picture has a red arrow pointing at the direction of the third bolt you need to remove
   
   
   Third bolt:
   
   
   
   
3. Position the drain pan since a little might drip, and remove the 8mm fill bolt. If it's seized, use a pipe to extend the allen, or a breaker bar if you're using a stubby hex.
   
   
   
   
4. Drain transmission, 10mm hex. Tip: Don't drop the drain plug. Once the transmission is done draining, screw it back on. This will prevent annoying dribbling during the next step
   
5. Remove transmission pan, the bolts are all T-40. I recommend starting from the front bolts, and leave one of the rear bolts as the last one. This is because there's a solid amount of fluid that stays in the filter, and once you tilt the pan, the filter releases it. If you start off at the front, it'll tilt towards the filter, and you can avoid having it run out and spill out the back:
   
   
   
   Pan removed:
   
   
   
   
6. Clean the mating surface off of any ATF and dirt.
7. Reinstall the transmission pan, hand start all bolts. Just get the bolts to catch so they don't fall/let the pan fall, do not actually torque them down yet. Start by using bolts 1 and 2 to hold the pan, then the rest, following the correct sequence:
   
   
   
   
8. Tighten pan bolts down to 10nm, make sure to follow the mentioned sequence above. Do not deviate from the sequence. I'd put down the drill for this part, you don't wanna mess it up and get a gasket leak, don't be lazy
9. Torque the drain bolt down to 8nm, you're ready to fill now.
10. Fill the transmission via fill port with your preferred method, shake bottle before opening. Don't fill it too fast or it'll look like it's full, when in reality you're just filling it faster than the transmission can handle. I use a $15 DIY version of the Motive Power Fill, makes the whole thing pretty much hands free and so much less messy. I'll likely post a DIY guide on making one yourself, stay tuned. If you don't want to wait, I used this video as a reference. Stop filling when ATF starts to come out of the fill port. Make sure it's a steady stream, since sometimes some will flow out due to turbulence or just from a bit of splashing. Wait until it's done dripping to proceed.
11. Follow the ISTA+ instructions for oil balancing. If you have ISTA+, it will walk you through the process. Just for clarification of the ISTA procedure though: ZF has confirmed that the wheels should not spin during the process.
    
    
    
    

For those who do not have ISTA+, you need some way of reading the transmission oil temperature reliably, such as via BimmerLink or OBD Fusion. This is what ISTA tells you to do:

1. Fill transmission until it overflows (already done if you followed my steps). Again, ensure that it's a small but steady overflow, and not just a couple drops.
2. Ensure parking brake is engaged, start car, immediately fill again until it drips. Wait until it stops dripping and reinstall the fill plug, no need to really torque it down yet. This is where a second pair of hands comes in handy, as they can start the car for you. If you have a power fill tool, this part is easy since all you do is let the fluid start flowing again.
3. Wait until RPM's fall under 900, and then turn off DSC completely by pressing and holding the DSC off button.
4. Foot on brake, shift car into reverse. Wait 10 seconds. Shift into drive, move shifter to the left and go into M1. Wait 10 seconds. Shift into M2, wait 10 seconds. Shift into park.
5. Rev to 2000 and hold it there for 30 seconds to fill the torque converter, and allow transmission to warm up to 40*C.
6. Once transmission is up to temp, open the fill port. If any fluid comes out, let it drain until it stops. Might still be a good idea to fill it until it starts coming out again, just to be safe.
7. If no fluids come out, fill until it does, then let it drain until it stops.
8. Reinstall with the new fill bolt. Torque to 35nm, I just made sure it was gudentite since it's a bit too crampedto get a torque wrench in.
9. Reinstall everything.

I used about 4.5 liters of ATF, the car holds 7. You won't get everything out, and I wouldn't try to as that's a very involved process, requiring you to empty out the transmission cooler lines and torque converter.

While doing this, if you're RWD I'd actually replace the mechatronic sealing sleeve, as that sometimes leaks. Need to do this with the transmission drained, so this is a good time for it. For AWD, there's not enough space without dropping the transfer case, so I'd just poke around and make sure it's not leaking, and if it's not, leave it. Pull out the sleeve, use some ATF to lube up the new one's o-rings, and push it in. It only goes in one way and one orientation, so if it's not going in, rotate it until it does. Push the plug back in and rotate it towards you (clockwise) until it solidly clicks.

Twist the tab towards the top of the car (counter clockwise), it'll unscrew itself. Pop it off, needs a bit of force.



You can see just how tight it is for xDrive owners, that big black mass to the right of the picture is the transfer case, the left is the transmission pan.



Note: Some video guides say to take an infrared laser thermometer to measure the pan temperature and go off of that. It will NOT work. The pan heats up significantly slower than the fluid will, so by the time the pan is up to temp you'll likely have overshot the fluid temp.