They do have a cover (though some call them a pan), it's just weld on rather than bolt on like a salisbury cover.
Actually they are thin, compared to the rest of the axle housing.

It's not uncommon for them to be holed. I welded one closed on a guy's rig some years back at Uwharrie.

 

I picked up one of these from L8 for my front diff...


It bolts into the bottom of the diff in the rear and has two tabs that weld on (not pictured) to either side of the front.

 

Sorry for hi-jacking the thread for a moment, but...

Tom,

I've heard you can do an emergency weld from a 24v rig, a set of heavy duty jumper cables, and a couple welding rods if you know what you're doing. (I don't and wouldn't try it myself.)

So, out of curiosity I have to ask...did you happen to have a welder with you, or did you do it from a 24v battery out of an ex-MOD truck?

Dave

 

Someone else there had an on-board power welder.
You can actually weld with 12v, ideally two batteries connected in parallel.

The 24v Rovers use dual 12v batteries connected in series, not 24v batteries.

 

My nice trail rash... you can also see where the track rod took a hit as well. The drain plug was busted as well, got a new one in there now.
I was going down a very steep hump and the underside of the front bumper brushed over a submerged rock and rolled it out of the ground, the diff and track rod took a hit. The rock lifted the front wheel off the ground and the truck rolled forward on the rock, making some expensive sounding noises.

 

Looks good Bundu...you receive the LR green heart award for damages done while 'froading!

By the way, I know that expensive sounding noise you heard...those were the benjamins leaving your pockets in double time