Mercedes-Benz recommends that you have the ball coupling assembled at a qualified specialist workshop. Only a qualified specialist workshop has the necessary specialist knowledge and tools to carry out the work required. You could otherwise incorrectly assemble the ball coupling or tighten the nut with the incorrect torque. This could lead to the ball coupling and the ball coupling carrier becoming detached while towing a trailer.
As a result, you could cause an accident.
Therefore, have the ball coupling assembled at a qualified specialist workshop.
If the assembled ball coupling has been permanently mounted on the vehicle, have the ball coupling regularly checked for correct installation and torque at a qualified specialist workshop.

WARNING
The ball coupling can be damaged if the nut is tightened on the ball coupling with the incorrect torque. This could cause the trailer to detach while driving and an accident could occur as a result.
Therefore, please observe the following:
- do not exceed the maximum permitted noseweight of the ball coupling, the trailer coupling and the trailer tow hitch.
- when installing, always use a retaining ring between the nut and the mounting surface of the ball coupling carrier.
- if the assembled ball coupling has been permanently mounted on the vehicle, have the ball coupling regularly checked for correct installation and torque at a qualified specialist workshop.
- check that the thread under the nut is of the correct length.

Mercedes-Benz recommends that you only use ball couplings tested and approved for use on Mercedes-Benz vehicles. This helps to avoid damage to the vehicle.
Observe the manufacturer's installation instructions if you use a ball coupling other than the one supplied.

Also observe the height of the trailer coupling and the trailer manufacturer's instructions.

Depending on the height of the trailer coupling, it is possible that the ball coupling will have to be rotated by 180° on the ball coupling carrier for correct installation. The assembly is otherwise identical.

– Insert ball coupling 1 through the hole in ball coupling carrier 2 as far as it will go.

– Slide retaining ring 4 onto the thread of ball coupling 3 as far as it will go.
– Screw on nut 5 as tightly as possible.

– With a torque wrench, tighten nut 6 to a torque of 516 lb-ft (700 Nm).
– Check that projecting thread 7 has the requisite length of 0.32 in (8 mm) beneath nut 6.
– Check the assembled ball coupling for correct installation.