BW 9 bolt In Out play
 

I was doing a regular inspection of the whole underside of my GTA and when I jacked the rear wheel to inspect the wheel bearings I noticed a small clunk sound on the passenger side wheel. I thought its the bearing so I went ahead removed the tyre to inspect further just to find out that the clunk sound is coming from in/out play not twisting. I hope I am explaining myself correctly....

My diff is a 9-bolt BW Posi which have their axle bearings held in place by 4x bolts and a plate (no c-clips). From what I could understand, the in/out play can still be bust bearing however it could also be that the retainer ring behind the bearing got dislodged or maybe was never installed properly. Am I understanding this correctly?
As I also do not know if the shaft is also held in place inside the diff, I did some further research and apparently these BW (aka. M78) have taper metal cones to achieve the limited slip and I thought that if they wear out, some in/out movement might also occur in the axle. Not sure about this theory either however I did check the amount of torque needed to rotate one of the wheels while the other is held stationary and I measured circa 80Nm. A post of this forum specified that anything below 35Nm would be an indication of worn cones which is clearly not the case.

Also to note that when I say in / out movement, I am roughly measuring 1/16' movement at the very maximum. As I said only on the driver's side.

Should I be worried? Is there an adjustment for this movement? Should I remove the axle and inspect something in particular?

Any help would be greatly appreciated. These diffs are not that well documented unfortunately.

Thanks

Re: BW 9 bolt In Out play
 

The axles are held in place by the tapered roller wheel bearing pressed onto the axle shaft, the pressed on retainer ring you mentioned and the outer plate with the 4 bolts. I don't recall how much in/out play mine had when I put it together with new bearings, but I believe it was none since it's a tapered roller bearing and any play would not provide the required bearing preload. There is nothing within the carrier that retains the axle in/out, only the outer retainer plates at the wheel bearings. The cones and spider gears are splined and the axles insert into them, but there are no retainers within the carrier for the axle shafts. It sounds like you may need new bearings. The axles can be removed without touching the carrier and without removing the diff cover.

Re: BW 9 bolt In Out play
 

Thanks for the explanation and the photos. My only doubt is related to the amount of acceptable play still. As you can see, there is the plate > seal > bearing > retainer.
Does it mean that the seal carries all the outward force inhibiting the axle shaft from going out? I can understand the retainer holding inward force but all the outward force is squeezing the seal against the bearing then?

Re: BW 9 bolt In Out play
 

If you zoom in on the photos, you'll see a ring on the OD of the roller bearing cage. That ring has a light press fit into the axle housing and helps to hold the bearing tight against the outer race that is also press fit into the axle housing. Yes, the seal is squeezed in between the outer retainer plate and the bearing, but with the additional press fit of the outer ring into the axle housing, the axle and bearing doesn't move in/out freely and maintains the preload on the bearing. You will need a slide hammer to get the axles out because of this.