2000 Ford Explorer Low oil in rear axle = ABS light?

Aside from the usual ABS light at ignition, I noticed the ABS light would come on and stay

on shortly after starting the Explorer. Other times it wouldn't come on at all despite

driving for 50+ miles at times. Used the ol hayne's manual to locate the rear axle ABS

sensor and crawled underneath the Explorer to make sure I could find it and check the

conenction. It was then I noticed what looked like a oil nipple on the driver side of the

rear axle, angled upward and towards the rear. There was a rubber hose connected to it and

stoppered at the other end, but that hose apparently broke off from wear and tear (feels

rigid and ome of the hose is still on the nipple). I also noticed what looked like some

fluid/oil having leaked out of the nipple. Not a huge amount, but enough to definitely

collect dirt and grime from the nipple and down the axle towards the ground.

There are no abnormal sounds from the rear end and it drives normally other than the ABS

light. The brakes work and there is no pulling. Front brakes are as warm as the rear brakes

as well.

Having said all this, I was wondering if the ABS light could be due to low oil/grease/fluid

levels in the rear differential. Should I be concerned with particles making it into the

rear differential due to this nipple being exposed? Any other concerns or recommendations?

I've used your website before and your advice has normally been very helpful.

Thanks for your time.

(BTW: Accidentally selected 4cyl. Edited to 6cyl)