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Discussion Starter #1 (Edited)
I separated the trans from the engine on my other project, a 2010 with 86k miles. I understand that the car was driving ok when I received it, so it was not in a failed state.

People have talked about how the slave cylinder leaks and to replace it if and when you drop the trans. I read that it gets the clutch and flywheel wet, but I've not come across a photo. Here is a picture. Thank you FTE, Getrag, and BMW.

Based on the April 2015 date code on the top harness on the SMG harness, this trans has been dropped before. I suppose this is what a leaky slave cylinder looks like. I guess it was not leaking that bad, I guess it could be far worse, the bellhousing is quite wet. It leaks like every other part on the car. Based on this, I second the advice given here on the forum to just replace the slave cylinder if the trans is dropped. I will be modifying the studs on the slave cylinder so that I don't have to drop the trans in the future to replace the slave.

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How do you plan on reversing the slave cylinder bolts? IIRC the nuts are pressed into the housing. Would be a good project if done right though.


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Discussion Starter #3 (Edited)
I recall someone on of the threads mentioned pressing out the studs. I can confirm this works great. I didn't bother taking pictures since this was very quick and easy for me. It took me longer to type this vs. doing it. I'll try to edit the thread title so others can find this too. Pictures will be uploaded next week when I get back. I removed the old slave and pressed out the old studs, I believe they are M8x1.25 thread and knurling at the base with a dog point nose to facilitate machine fastening at the plant . The slave cylinder seems to be anodized aluminum. The studs can be pressed out quite easily with a press. The diameter of the hole in the bellhousing is the same as the through hole that was in the slave cylinder. All you do is then swap them.

This joint really just for clamping the cylinder to the bell housing, there are not any unusual loads or forces to worry about. They designed this for ease and speed of assembly, and it makes sense why they did it this way. If you did over-torque this when swapped (stud pressed in the bellhousing) you will damage the bellhousing and that will be bad since the bellhousing is not designed to be a service item, but the slave cylinder absolutely is a serviceable part.

DIY Steps to press out studs (it's not as complicated as it sounds):
I recommend starting with your new slave cylinder, you can do this anywhere, you can even press these out and then give to the parts to your indy to complete the cylinder swap out.

1) Use another M8 nut (I prefer not to use the old nuts for this) and run it down on the tip of the stud until all the threads on the nut and stud are engaged. Do not run the nut all the way down, as that will prevent you from pressing the stud out.
2) Use a 13mm short well socket (I think 13mm was the socket size) as a base to press the stud out. You can use another larger socket like a 16mm to fit around the base of the stud for support.
3) Press the stud out of the slave cylinder. As a crude alternative (not the recommended method) you could just try hammering out the stud by smacking the top of the 13mm socket.

4) Put the stud in the bell housing, make sure you orient the tip so that it is now facing rearward. Put a washer and M8 nut around the tip of the stud and HAND tighten -with your fingers- as much as possible so the knurling will start to interfere with the hole.
Check to make sure it is going in square (the stud should be perpendicular the surface of the hole)
5) Smack the back of the stud, ideally with a brass or metal rod and a hammer so that the stud seats itself in the hole. The hole is recessed inside the bellhousing so you likely can't smack it square without a rod or piece of wood.
6) Tighten the nut down with a deep well socket so that it "self presses" itself into the bell housing as you tighten the nut. The knurled section of the stud has to grab and bite the bellhousing as you start tighten it other, that was the reason for step 5. If you allow the stud to also rotate you will have messed up the interference fit. This might happen if you just carelessly run down the nut with impact.
7) Run down that nut until the stud bottoms out against the bellhousing. Stud is now pressed in.
8) Remove the M8 nut and washer. You now can install and remove the slave from the outside of the trans, no need to ever drop the trans to remove the slave.
9) Install a new slave cylinder. Torque nuts to 25Nm. Note that this assumes that the studs are already pressed out of the new slave, otherwise you can't install it since the through holes in the bell housing now have studs coming out (you have a sword fight:LOL:).
 

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I recall someone on of the threads mentioned pressing out the studs. I can confirm this works great. I didn't bother taking pictures since this was very quick and easy for me. It took me longer to type this vs. doing it. I'll try to edit the thread title so others can find this too. Pictures will be uploaded next week when I get back. I removed the old slave and pressed out the old studs, I believe they are M8 thread with dog point nose to facilitate machine fastening and knurling at the base. The slave seems to be anodized aluminum. The studs can be pressed out quite easily with a press. The diameter of the hole in the bellhousing is the same as the through hole that was in the slave cylinder. All you do is then swap them.

This joint really just for clamping the cylinder to the bell housing, there are not any unusual loads or forces to worry about. They designed this for easy and speed of assembly, and it makes sense why they did it this way. If you did over-torque this when swapped (stud pressed in the bellhousing) you will damage the bellhousing and that will be bad since the bellhousing is not designed to be a service item, but the slave cylinder absolutely is a serviceable part.

DIY Steps to press out studs (it's not as complicated as it sounds):
I recommend starting with your new slave cylinder, you can do this anywhere, you can even press these out and then give to the parts to your indy to complete the cylinder swap out.

1) Use another M8 nut (I prefer not to use the old nuts for this) and it down on the tip until all the threads on the nut and stud are engaged. Do not run the nut all the way down, as that will prevent you from pressing the stud out.
2) Use a 13mm short well socket (I think 13mm was the socket size) as a base to press the stud out. You can use another larger socket like a 16mm to fit around the base of the stud for support.
3) Press the stud out of the slave cylinder. As a crude alternative (not the recommended method) you could just try hammering out the stud by smacking the top of the 13mm socket.

4) Put the stud in the bell housing, make sure you orient the tip so that it is now facing rearward. It will be just laying there until the next step
5) Smack the back of the stud so that it kind of seats itself in the hold
6) Put a washer and M8 nut around the tip of the stud. Tighten the nut down with a deep well socket so that it "self presses" itself into the bell housing as you tighten the nut. The knurled section of the stud has to grab and bite the bellhousing as you start tighten it other, that was the reason for step 5. If you allow the stud to also rotate you will have messed up the interference fit. This might happen if you just carelessly run down the nut with impact.
7) Run down that nut until the stud bottoms out against the bellhousing. Stud is now pressed in.
8) Remove the M8 nut and washer. You now can install and remove the slave from the outside of the trans, no need to ever drop the trans to remove the slave.
9) Install a new slave cylinder (with the studs pressed out, otherwise you can't install it since the through holes in the bell housing now have studs coming out)
Great write up, I will do this the next time I have to lower the SMG.


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Discussion Starter #5
I also think the slave cylinder should be rebuildable, if someone can get their hands on the right seals from FTE. I find it hard to believe the aluminum housing somehow failed. If I can get my hands on another one, I'll slice it in half.
 
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