Back the summer before last, I changed out the axles on my car. When I did so, I could Not get the circlip in for the right-side axle. This was before I had the service program to tell me of it's importance, and my technical help Was from a seasoned veteran but his health was not the best at that time... He said if I couldn't get it in, not to worry about it. I see now that we were wrong...

W123 240D rear axle spacers?

Now, the reason for me posting this is I am hoping to take a rough assessment of the situation before I open the diff back up again; what am I likely to find in your opinion?

Particulars; I've driven about 7K miles this way. I have a vibration on the RR that comes on at about 45-55mph, is it's worst at 55-60, and never goes away at any speed higher than that, it just lessens. The vibration is less likely to come on if I can keep a load on it and stay below 55, but as soon as I slow or coast, it will begin. THIS is the bit that tuned me into the fact that the lack of the clip was the cause for the vibration... EDIT--I should add, the rear springs on this wagon are weak, but the SLS is working. It sits a little lower than it should, and that may be an Added contributing factor here.

I had no idea there were different sized shims... I am not even sure I have a shim in there, honestly...

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1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)