Torsen Groan?

[jaychen]

When doing a tight right hand U-turn I can hear what can only be described as a groan. It sounded as if it was coming from rear right area. It only occurs under load, when coasting while doing a U-turn, no noise is present.

I went ahead and checked wheel bearings anyway (all round) - all good. No play in centre bearing. Changed the gearbox and rear diff oil (fuchs sinto), noise still occurs. There is no harsh noises, just a slight groan. Oil looked fine upon inspection, little to no star dust. No chunks or noticeable metals.

Im fairly sure it's either coming from my centre diff or my rear diff. Has anybody else encountered this slight 'groan' similar to the symptoms i'm illustrating ?

[MacFady]

See subject line. Makes sense, your rear right wheel would barely be rotating while making a tight right U-turn compared to how much your front left is rotating. And yes, I experience that, and have always, every time I make a similar maneuver.

[UCFQuattroguy]

It's normal. A Torsen will try to keep the front and rear rotating at the same speed until the difference in torque acting upon it exceeds whatever the TBR is set (~2:1 on the OE setup). Once this happens, the Torsen will begin to allow the front/rear to rotate independently. When in gear and applying some throttle, there is a load going through it. That groan is nothing more than the gearset inside the differential rubbing on each other. It's quiet when not in gear because you're not putting any load through it.

[okkim]

A Torsen will try to keep the front and rear rotating at the same speed until the difference in torque acting upon it exceeds whatever the TBR is set (~2:1 on the OE setup). Once this happens, the Torsen will begin to allow the front/rear to rotate independently.

That is totally wrong. Torsen does not "open" if the torque difference of the axels is big.

"The Torsen differential works just like a conventional differential but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR).[3] When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential."

https://en.m.wikipedia.org/wiki/Torsen