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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Torque setting confusion (DMF/clutch/gearbox)



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      07-30-2018, 05:23 AM   #1
tadaska
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Torque setting confusion (DMF/clutch/gearbox)

I'm going to be replacing my dmf/clutch etc tomorrow and I'm going over the torque values but there is something here I don't get.

For the pressure plate it says: M8 8.8 24Nm, M8 10.9 34Nm, ZNS bolts stage 1 15Nm and stage 2 is further 90 degrees.

Looking at realoem and it say my pressure plate uses M8x18-10.9-ZNS3 bolts. At first I thought I need to use the M8 10.9 setting (34Nm) but then it says it's ZNS3 so maybe I need to use the ZNS setting? I'm confused.

The same with the gearbox-2-engine bolts. I have torque specs for hex or torx bolts of various sizes (M8 M10 M12) which would be fine but on realoem some of the bolts have ZNS3 on the end. But I don't have a ZNS spec for the gearbox bolts.

Anyone can shed some light on this?
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      07-30-2018, 06:24 AM   #2
matt_s
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I believe ZNS is the anticorrosion coating, so Id assume your torque setting needs to be derived from the hardness ie 8.8 or 10.9. Take some photos as Ill be doing mine soon! 😀
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      07-30-2018, 02:27 PM   #3
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8.8/10.9 relates to the bolt material ultimate & yield strength, not hardness.

I would say if you have ZNS coated bolts you need to use the ZNS specific tightening spec.

Are the torque specs for the gearbox-to-engine bolts the same as the torque specs for the dmf/clutch bolts for a specific size & grade (non ZNS coated)?
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      07-30-2018, 02:41 PM   #4
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Quote:
Originally Posted by gaz_ball View Post
8.8/10.9 relates to the bolt material ultimate & yield strength, not hardness.

I would say if you have ZNS coated bolts you need to use the ZNS specific tightening spec.

Are the torque specs for the gearbox-to-engine bolts the same as the torque specs for the dmf/clutch bolts for a specific size & grade (non ZNS coated)?
Pressure Plate M8 8.8=24Nm 10.9=34Nm ZNS spec available
Gearbox-Engine M8 Hex=25Nm Torx=22Nm ZNS spec not available

But according to realoem some bolts are ZNS: https://www.realoem.com/bmw/enUS/sho...diagId=23_1034
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      07-30-2018, 03:44 PM   #5
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I was hoping they'd be the same so you could apply the ZNS spec from the pressure plate bolts to the gearbox-engine bolts. Are the pressure plate M8 bolts hex or torx?
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      07-31-2018, 04:15 PM   #6
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Quote:
Originally Posted by gaz_ball View Post
I was hoping they'd be the same so you could apply the ZNS spec from the pressure plate bolts to the gearbox-engine bolts. Are the pressure plate M8 bolts hex or torx?
I ignored the ZNS spec and used the M8 10.9 spec (34Nm) for the pressure plate. And for the bell housing I just used the air ratchet.
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