While I'm at it I might as well reseal the rear cover, too, since the lube is due to be changed anyway. I know that my rear axle is a Ford 8.8 non-limited slip, and I see that pre-cut rubber gaskets are plentiful for those. The service manual says the front axle is a Dana 35, and I found a gasket to fit that at Summit Racing (though the applications only list AMC and Jeep vehicles).
I got quite a few service records with this vehicle and from those I see that in December 2005 the front pinion seal needed replacement and that in May of last year the driver's side front axle seal needed replacement. I believe the diff cover has to be removed for both of those procedures so it is possible that it was not resealed correctly or that the replacement seal was just barely sufficient.
I also have two months of powertrain warranty left from the dealership, but they are 100 miles away and I'd hate to burn a half a tank of gas there and back if this is a relatively simple job. Thoughts?