Rear locking differential 1988 90Q

Radek radek at
Tue Aug 7 08:28:50 PDT 2012

So now that the diff is out, we can clearly see the cause of it being locked all the time.  As I suspected, the plastic vacuum actuator has broken off at one of the three screws and is moving around a bit.  I used a vacuum pump:  it seems to be holding vacuum when the "on" side (yellow striped hose) is activated, but doesn't hold it when the "off" side (blue striped hose) has vacuum applied.  This is odd, because I would expect a single membrane inside, so if it's broken there would be no vacuum held on both sides.  To put things differently, the actuator has enough strength to engage the lock, but not enough to disengage it.

I would like to take it off the diff to clean, inspect and repair/replace.  Here's the question:  how do I separate it from the diff?  The actuator arm has a pin at the pivot point, but it seems to be permanent.  Can I pull the arm out of the actuator or out of the differential perhaps?  Bentley does not offer any help (or I haven't found it).


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