Disconnect the vac lines at both front knuckles and plug them with golf ball tees,use a vac pump and apply vac to the outlet port of the vac solenoid for the hubs(located behind the battery)should hold vac-if not replace all the vac lines from the solenoid to the hubs-these are known to get pin holes in them.Check the vac check valves to see if they hold vac in one direction-if not ,replace the vac check valves.Vac test the vac reservoir,it should hold vac-if not replace the reservoir(located under the battery box).Also,with the hubs ratcheting,there will have been damage to the actuator and hub teeth,so replacing those parts were not money wasted.
Hope this helps with your diagnosis.
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