After 60+ years with this truck you'd think it had done just about everything it could to surprise me, but a couple of days ago it found a new trick.

We had one of those fake spring days here in NE Indiana so I took the truck out for a run after I did a couple of things that had been waiting on warmer weather.

I had also cleaned out the "car barn" to get rid of winter stuff so I had a nice clean floor for a change. I pulled the truck into the barn and it piddled on the nice clean floor. It was differential lube and my first thought was"Oh my goodness, I have a leaking pinion seal" - or words to that effect. So, I cleaned up the mess and crawled up under the rear axle and saw that the leak was coming from the top of the driver's side axle.

There is a vent there and differential lube was blowing out through that vent. No, its never done that before and no, I haven't added any lube to the differential over the winter. I was able to unscrew the vent and it seems to be OK as far as I can tell - just a little threaded fitting and a nipple with a loose cap on it. There is no sign of any kind of spring or check valve action in it.

I know there is a vent on front differentials on the CJ's, probably one on the Dana rear axles. Is there any secret to how they work; springs or such?

I put it back together and when I get back to it I am going to drain the differential and see just how much lube there is in there. It's not making any noises or acting up - but I wonder why it's throwing that much lube around all of a sudden and losing it through the vent?

Any ideas?