Rear-end failure modes?

[Mike Grace <mgrace@domain.elided>]

Most knowledgeable sources I have talked to praise the strength and 
reliability of the Alfa live-axle rear end. I'm trying to figure out if the 
differential is toast in my 74 GTV. Recently my mechanic noted that my rear 
wheel bearings seem to have way too much play compared with normal. 
Substantial play is felt when the wheel is grabbed (at 12oclock and 
6oclock) and rocked gently. Having done this job before, I decided to 
tackle the axles removal myself and have a machinist R&R the bearings and 
retaining collars. However, I just drained the oil from mine and the 
magnetic plug was filled with a fine "silt" for lack of a better word. 
Further, with the wheel off, I find almost no play when the disc brake hub 
is grabbed and rocked. The Panasport wheels seem to be on tight, I checked 
the depth of the wheel cap nuts against the length of the studs (0.1 in. 
clearance), I checked with the original steel wheels and nuts, and it's 
exactly the same. Is it possible for the inboard bearings (i.e. in the 
differential) to go bad and the play I'm detecting is not at the wheel 
bearing but at the inboard end of the axle? Something is definitely too 
loose back there and it may be the source of the driveline vibration that's 
been haunting me for about a year now. Any diagnostic tips?

Mike Grace
74 GTV
Santa Barbara, CA

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