Center Diff locking problems in 87 4KCSQ

[rob_duvalle@co.washington.or.us]

Thanks everyone for the help on the "clunk".  I am going to replace the 
control arm bushings and ball joints this weekend and cross my fingers.  

On another note, When I purchased the car, both the front and rear diffs were 
not functioning.  I checked the vacuum lines and they checked out.  The 
cuplrit was the servo units (both would only move one direction and not the 
other). Attempted to find used units to no avail and priced new ones from Audi 
were major $$$$.  Found an intermediate solution, mercedes door regulators are 
almost identical (except for missing one of the bolt holes), and were about 
1/3 the price.  I installed both of them and now the rear diff works great.  
The front, on the other hand is still stickey.  It will engage _most_ of the 
time at different speeds but when it does it makes a loud "thwang" and you can 
feel it shake the car.  Once it engages, it does fine.  Disengaging it can 
only be done by completely stopping the car and going into reverse and coast a 
bit backwards.  Others I have spoken with seem to think it is internal in the 
diff from possibly years of non-use and rust.  Any other ideas.....?

Thanks in adavance for the help

Rob DuVAlle, rob_duvalle@co.washington.or.us
87 4000CS