There was never a factory option for a front limited slip. In fact, the factory has always used Dana Trac-Loks, and I don't believe there is a Trac-Lok available for the Dana 30 front axle.
If the friction modifier lube additive has worn out in the rear, the clutches may grab and cause some ratcheting, or tire chirping. Head to a dealer, buy a bottle of friction modifier, and put that in. Of course, it would be better to change the diff lube at the same time, but at least do the modifier because if you don't, you risk wearing out the clutches.
Although I have to say that it sounds from your description that you may have lockers rather than a factory limited slip.