I'm running a simple analysis to measure the torque transmitted to a contact patch on a wheel in SW Simulation. In the image below I apply a 134 Nm torque to the shaft face about its axis, the shaft transmits torque to the wheel which has a fixed patch at its base.
The problem is that when I'm checking the reaction forces and torque, I'm getting a torque of 138 Nm.
I expected to get a bit less since the contact definition of the gear teeth is No Penetration with 0.2 coefficient of friction. So I'm wondering if it's just a margin of error or something.
In the image below, the torque is measured from a point on the axis