There are multiple threads on this. Libertys were known to have this issue. The speed sensor in the back on top of the diff is not the culprit per se but it's the wiring harness (pigtail) that's the issue. If you go to the dealer you can request the rear speed sensor and pigtail for you model year (should be universal for most years) and cut out the old and put in the new. Problem is the wires will fray apart on the inside because of it bending so much. What I did to solve this is get the parts I mentioned above, bought some liquid tape, and wire looming (I think that's the technical name) and sealed everything so that no water got in and corroded my connections. What I did for the wires was got some heat shrink connectors that are water proof. When you heat them up, they seal because the sealant melts around the wire making sure no water will get in. Then I taped them up for extra protection and used liquid tape (can be found at Walmart or your auto parts store) I also flushed the differential and put new gear oil in. Works better and fixed my issues. Haven't had a problem since. Best of luck!
PS, l get some extra wire and make the pigtail longer so the wires don't have a harsh bend at the connector.
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