DIY: MT Fluid Change for F8X w/ Pics

[maniz]

I looked around for an MT gear oil replacement DIY but couldn't find it; just the BMW official document, so thought to take pics while performing the service on my 2018 F82 yesterday. I don't know whether pre-LCI models have any variances but I doubt they do. It is a straightforward job as you will see.

Caution: This is meant as a general set of guidelines. You assume all risk by attempting the procedure.

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Required:

- T50 socket; short/slim if possible. EDIT: Use 8MM (5/16 SAE) Hex instead. Thanks to members who pointed it out.
- 8mm socket.
- 10mm socket.
- Socket wrench; slim if possible.
- 3" socket extension.
- Optional: Electric impact driver to speed up the cover removal.
- 1.6L of BMW MT Gear Oil. 75W-80. Part# 832 2223 9654
- Fluid transfer pump. I used OTC 2359 manual pump, but almost any will do.
- Drain pan.
- Equipment to lift and safely support the vehicle.
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Process:
Refer to attached photos for reference


- Raise and support your car to keep it in place.
- Locate the underbody cover over the transmission tunnel. It is just behind the metal belly pan, directly under the driver's seat (LHD). Refer to photo below for the shape of the piece.
- It is held together by ten 8mm screws and one 10mm nut. The picture below notates the 8mm with yellow arrows and the bolt with red. The front of the piece is tucked under the belly pan.
- Best to remove the recessed screw at the end. It, combined with the tuck-in under the belly pan, will keep the cover in place while you go around removing the screws.
- Remove the cover and put it away.
- Refer to the pic below to locate the drain and refill/check bolts.
- You will loosen the fill hole first as common sense dictates. IMPORTANT: Clearance is tight here, hence short socket and / or slim wrench heads are helpful.
I don't believe the bolts have true torx heads; the shape is slightly off compared to any torx head I've seen, but T50 worked for me. If you know what they are, do say so below to help others. EDIT: Use 8MM or 5/16 Hex instead
- They were torqued VERY hard at the factory My car is brand new (5.7K mi) and has zero corrosion, yet removing them took some muscle, so be very careful not to round your heads if your car is older and bolts are showing signs of corrosion. Mine were a bit marred in the removal process, so I will replace them at next service.
- One the fill bolt breaks lose, leave it in place and remove the drain bolt.
- Fluid will gush out; let it drain until the drips stop (30 min or so). It should look clear and new; the transmission is a sealed unit so the fluid never gets dirty.
- Reinstall the drain bolt. There is no gasket to replace. I should've looked up the torque setting, but torqued it by feel instead. As I said, it was extremely tight from factory, so I tried to get it back to that level.
- Remove the fill bolt.
- Using your fluid transfer pump, suck up the clean fluid from one of the bottles, insert the transfer tube into fill hole and transfer fluid into it.
- Keep at it until fluid starts to drip out of the fill hole. That spot serves as both the fill and level-check location. Once it drips out, you know the transmission is full. You should need almost exactly 1.6L as BMW states in the official guide. If you used the pump I linked above, it should be about 2.5 pumpfulls since that one holds 0.6L.
- Once the drips stop, re-install the fill bolt and torque to factory spec or go by my "shade tree mechanic" spec and get it done tight. No gasket here either.
- Start the car and holding the clutch in, gently row through gears several times while the engine idles. Then turn it off and check the two bolts underneath for leaks.
- If all is well, replace the cover and lower the car.
- Revel in your newly silky-smooth shifting. The difference is especially obvious when the transmission is cold; no more clunks and thunks.
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Enjoy!

[Nothing]

Nice work. Thanks for this. I'm sure it'll be added to the DIY list.

[Brasko]

Great write up! I'm sure all the 6MT owners like myself will appreciate the pics and step-by-step instructions when it comes time to change out the transmission fluid.

[Canuck12]

Thanks for this. My 2015 has 23,000kms but third gear is a bit notchy/clunky feeling.

Planning to Motul as I have had really good experience with the 300V in my motorcycles.

[clutchdj]

So the million dollar question: Were there any visible metal shavings and/or did the fluid appear to look like a galaxy? TIA

[Canuck12]

Originally Posted by clutchdj

So the million dollar question: Were there any visible metal shavings and/or did the fluid appear to look like a galaxy? TIA

If you have any concerns about metal content, drain the fluid into a funnel, but keep a paint strainer and a small magnet in the strainer, this will filter and pick up any ferrous content. Works on engine oil as well

[maniz]

Originally Posted by clutchdj

So the million dollar question: Were there any visible metal shavings and/or did the fluid appear to look like a galaxy? TIA

Not a galaxy, thankfully! But there were a few tiny metal flakes at the bottom of my drain pan; like medium-sized grains of sand, after I poured the used oil out of it.

[FC]

Originally Posted by maniz

I don't believe the bolts have true torx heads; the shape is slightly off compared to any torx head I've seen, but T50 worked for me. If you know what they are, do say so below to help others.
- They were torqued VERY hard at the factory My car is brand new (5.7K mi) and has zero corrosion, yet removing them took some muscle, so be very careful not to round your heads if your car is older and bolts are showing signs of corrosion. Mine were a bit marred in the removal process, so I will replace them at next service.

They may be using double-square screws.



They are not Torx but people often think they are. They are meant to allow more toque than Torx.

I know VW uses them to secure the head to the engine block. I learned this while helping replacing a head gasket in the middle of a Lemons race. The bits are not easy to find locally, and out of fear I ever get caught with a car on my lift without the right tool, I immediately bought a a set.

[maniz]

Originally Posted by FC

They may be using double-square screws

That could be it, or a Torx Plus. I didn't know there was such a thing. I believe I took a photo of the drain bolt head. I'll look for it.

[gatorfast]

Can anyone confirm what type of bit is needed for the drain/fill plugs? I may attempt this when I change my oil next.

[Sidebrowns]

Originally Posted by gatorfast

Can anyone confirm what type of bit is needed for the drain/fill plugs? I may attempt this when I change my oil next.

I did this a couple days ago and on mine the plugs took a 8mm Allen bit. As far as I can tell this part hasn't changed during the F8X run and is shared with many other cars as well so I assume we should all have these 8mm hex plugs.

[wsccsw13]

Did mine a couple days ago. Yes, 8mm hex for drain bolts. Always loosen the fill bolt first. Torque is 43 Nm...they were much tighter than that from the factory.

[elinstylez]

Has anyone noticed smoother shifting following the fluid change. I’m thinking about getting this done.

[gatorfast]

Originally Posted by elinstylez

Has anyone noticed smoother shifting following the fluid change. I’m thinking about getting this done.

I think if anything its mainly a placebo effect. The same way your car seems to drive better after a fresh oil change. I have always replaced the manual trans fluid in my bimmers around 50k miles but honestly I cant say the shifting felt materially different afterwards. Of course, shifting was never an issue beforehand so its not as if there was something to correct.

[hlm2c]

Originally Posted by gatorfast

I think if anything its mainly a placebo effect. The same way your car seems to drive better after a fresh oil change. I have always replaced the manual trans fluid in my bimmers around 50k miles but honestly I cant say the shifting felt materially different afterwards. Of course, shifting was never an issue beforehand so its not as if there was something to correct.

On the old fluid, did you have issues getting into first gear from neutral, like at a stop light from time to time? I understand that's just the nature of BMW transmissions, but I would like to know if that got any better once you changed your MT fluid. If anyone that swapped their MT fluid wants to chime in... Also assuming that this is you guys first MT fluid change and no one changed their MT fluid at break in as it's not covered.

[MAddict]

To OP: Thanks for posting this, I used your guide to DIY transmission fluid change yesterday.

One point I noticed that may help others: A 5/16 in Hexagon bit fit both the fill and drain transmission plugs perfectly, and did not mar up the plugs at all. The T50 bit also fit, but would mar up the plugs.

Here's a comparison photo:

[jmciver]

Originally Posted by MAddict

To OP: Thanks for posting this, I used your guide to DIY transmission fluid change yesterday.

One point I noticed that may help others: A 5/16 in Hexagon bit fit both the fill and drain transmission plugs perfectly, and did not mar up the plugs at all. The T50 bit also fit, but would mar up the plugs.

Here's a comparison photo:

It was mentioned a few posts up that an 8mm allen worked without issue. That is what I used, also without issue.

[maniz]

Originally Posted by MAddict

To OP: Thanks for posting this, I used your guide to DIY transmission fluid change yesterday.

One point I noticed that may help others: A 5/16 in Hexagon bit fit both the fill and drain transmission plugs perfectly, and did not mar up the plugs at all. The T50 bit also fit, but would mar up the plugs.

Here's a comparison photo:

Many thanks to you and everyone else who made the correct suggestion. I knew I had to be wrong; I guess I just didn't notice it when I did that.

First post edited above to reflect the same.

[robertg]

Is it recommended to change the drain and fill bolts like on the diff?

[jmciver]

Originally Posted by robertg

Is it recommended to change the drain and fill bolts like on the diff?

No, not required for the 6MT transmission.

[henrylee]

Thank you

[elinstylez]

Originally Posted by gatorfast

I think if anything its mainly a placebo effect. The same way your car seems to drive better after a fresh oil change. I have always replaced the manual trans fluid in my bimmers around 50k miles but honestly I cant say the shifting felt materially different afterwards. Of course, shifting was never an issue beforehand so its not as if there was something to correct.

Reporting back to say it feels exactly the same after doing it lol. But it provided peace of mind after buying my car second hand.