YFCM Carbon Driveshaft Installation Tips

YFCM Carbon Driveshaft Installation Tips

"The installation of the YFCM carbon driveshaft was relatively straight forward - yet it has new mission-critical information that we were never made aware until I started chatting with M.Lee at YFCM.

I highly recommend professional installation. A lift will make the job a whole lot easier too."
- Matt

Preliminary checks.

Inspect & Replace worn bushings and mounts!

If your bushings and mounts are worn - I highly recommend you change them. 6spd guys should be mindful of wheel hop on hard launches.

Recommended hardware. 

  • 1x Flexdisc "guibo" (SKU:  26112282573)
  • 1x Balanced CV flange / Diff bolt (SKU: see below)
  • 5x Standard CV flange / Diff bolt (SKU:  26117526322)
  • 3x Self Locking Nut for Guibo / Transmission flange (SKU: 26127536563)
  • 6x Hex Bolt for Guibo / Transmission flange (SKU: 26117527475)

Notes on balanced bolts. 

Your OEM driveshaft is carefully balanced at the factory and has a few versions. 

BMW uses a colored line on the driveshaft flange to indicate the balancing method used and the specific balancing bolt hole. 

Prior to September 2009 production date, the balancing was using washers on the marked hole. After 09/09, colored balancing bolts are used. My 2012 M3 uses the original diff from the factory.

  1. The blue marking indicates the black bolt (SKU: 26112284154)
  2. The yellow marketing indicates the green bolt (SKU: 26112284153)
  3. If your differential has white marking, then you're in luck: regular bolt it is. 

My diff had a blue line: It required the Black balanced bolt. 

Installation Steps.

You need to remove the center exhaust bracket, disconnect 02 sensors off the exhaust and remove the entire exhaust systems. 

The OEM steel driveshaft and center support bearing can then be removed. 

The transmission then needs to be supported for the transmission mounts to be removed.

It is required for the transmission to be lifted upwards within the tunnel to give as much clearance as possible to fit the 1 piece driveshaft along with the wrenches needed to torque down the flanges. 

It's a tight fit! Some tips and tricks. 

We needed to lift the transmission all the way up with the engine supported.

We also loosened the differential bushings and pried off them to get the YFCM to fit.

It's a tight, precise fit. 

Balanced Differential & CV Flange Bolt 

I chatted before about aligning the balanced CV / diff bolt colored in black with the blue mark on the diff but took a clearer picture this time around.

Final Checks. 

If you installation does not come within the specifications listed below, you may have worn bushings across the drivetrain.

Telescopic Flange Measurements

The picture below shows something new.


The CV flange is telescopic and allows for some play for the rubber bushing in the powertrain such as the engine mounts, transmission mounts, diff and subframe bushings.

As the 1 piece carbon tube design is engineered to flex and move with the drivetrain, YFCM carefully engineered the tube length to match with the CV flange.

It must have a 64mm / 2.52 inches distance between both points pictured. 

Carbon Tube Clearances

Carbon tubes are still larger than steel driveshafts - and more susceptible to being damaged by screws and bolts that are at the top of the tunnel.

Careful attention to clearances and free range of movement of the tube must be validated. 

There are 2x bolts and 1x screw by the CV flange that are to watch for.

There should be at least 20mm / 0.8 inches separating the tube from any physical element across the driveshaft valley. 

You need to meet these clearances before completing the installation as it may otherwise lead to catastrophic failure of the tube. 

 


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