1988 Jeep Wrangler

1988 Jeep Wrangler 6 cyl Four Wheel Drive Manual

My 4wd does not engage anymore. I have replaced the carburator, 4wd vavuum switch, 4wd actuator, and checked all of the vacuum lines (which are all good), I checked the check valves (which are all working properly). The transmission is responding like it should.I am at my wit's end. I spend more time under my jeep than I do in it. Do you have any idea why my 4wd is not engaging?
February 6, 2010.

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