25072 Faulty ADC value of rear speed sensor ( Am I right? )

[titus]

  Last year after 4000km round trip in the Alps, at some stage i got the unwilling warning red light triangle wit the flashing ABS red warning as well. ( I own a 2005 r1200gs  ). Well at the beginning i checked the sensor wire hoping for a bad connection , but it wasn't that. I took out the rear speed sensor and i noticed metal residual build on the magnetic part of the sensor. I clean it and everything was back to normal. But after a while the warning light came again. But this time i already had the GS-911 unit, and i got the error code.
    Conclusion : Due to the excessive wearing of the back unit drive, the metal residual build on the magnetic part of the sensor is to big and it became very hard for the sensor to read values from the abs stripped wheel ( inside the rear unit drive ).
    Theory : This excessive wearing is because of a poor lubrication of the components inside the rear unit drive. Either a bad lubrication at the transmission wheels, either a driving constant  at high speed ( highway ).
   I believe that the the components of the rear drive unit, are only coated with a strong steel material and after a while this strong coat it goes away and here it comes the trouble.

  Am I right?

[Jughead]

Hi Titus

The metal bits inside the final drive are most likely bearing bits from the pinion shaft.

This is usually caused by a lack of maintenance on the drive shaft spline, which then in turn places undue pressure and stress on the pinion bearings. (as well as the drive shaft UJs)

The crownwheel and pinion gears themselves are incredibly hard and rarely fail.  When they do, it is usually as a result of bearing bits ending up in the oil and in turn between the running faces of the gear teeth.

Here is a typical example of a failed bearing.

[titus]

This is how it looks my speed sensor. 98000 km , oil changed at every 30000. Does anyone have the same problem? I checked today, not any play at the bearing but still a silvered color of oil.

[Jughead]

How did you check the bearing?  Have you dropped the Final Drive to check the pinion play?

Checking for play on the wheel does not help as the large bearing that causes the rear wheel play actually sits outside the seal and not in the oil.  What you see there come from the pinion bearings.

[titus]

 Thx a lot Jughead, it make sense what you suggest. I will order the parts tomorrow. Hope i will manage to change. Do you think that it will be probably better to change all the bearings from the final drive ? Once it is apart it will be a chance to do so ( i do not have any idea how many km those bearings should last)

[Jughead]

Thx a lot Jughead, it make sense what you suggest. I will order the parts tomorrow. Hope i will manage to change. Do you think that it will be probably better to change all the bearings from the final drive ? Once it is apart it will be a chance to do so ( i do not have any idea how many km those bearings should last)

Hi Titus

Yes, it is essential to replace all bearing and seals at the same time.  Any metal bits in the oil, which were not picket up by the sensor in your photo, will be interfering with all the bearings that run within the oil.  So all the bearings will show excessive wear patterns and should be replaced.

However, just be aware that special tools are required to dismantle and re-assemble the final drive.  If required, I can provide you with a complete list of part numbers for the parts required.  Only one of the bearings can be purchased as an after-market part.  The rest are all BMW specific.  You can purchase the seals at virtually any bearing supplier, but only use Viton seals.

Have a look here for the strip-down procedure: http://www.roamafrica.co.za/forum/index.php?topic=2455.0

[titus]

  Hi, i already order the OEM parts including seals. I will have it here on next week . I do have to build the board and the special 331711 tool to  take out the pinion drive. I will see what i can improvise next week. Thx for tips, much appreciated. If you ever come here in Transylvania you are more than welcome

[Jughead]

[emoji106]

[titus]

The special tool done today