It doesn't always set a fault code, as it's not seeing a fault! Have you tried light acceleration up a small gradient, it can be quite difficult to feel, but once you can detect it, you will always feel it.
A very light shudder through the car, almost like it's had a single misfire event. The harder you drive, the more liable it is to transfer torque to the front wheels to prevent rear wheel-spin. This will emphasize any faults in the system.

Sent the TSB.

Tony