Is it safe to 'not' have a rear axle vent on my '78 F250 460 C6 rear wheel drive?

 

No, you need a vent . you'll build pressure in there when it's hot and push oil out your seals.

 

You need a vent.

 

Where can I find one? Either I don't know what to call it to identify it, or I haven't yet been able to find it on a part website.

 

it's just a piece of hose that goes on where your T in the brake lines is fastened.

 

What happened to the hole where was a vent screwed in?
Ford one. Smooth part goes through the T or Y where left and right brake lines join to rubber brake hose from frame. Just run a fitting hose from vent up to frame, maybe put a turn down on hose end, zip tie to frame up high.

 

On the end of the hose put a gas filter to keep junk out
Dave ----

 

Ok, that makes sense guys! Thank you again. Oh, tbear853, I will have to look again, but I threw old stuff away too soon without recognizing what it was or it's function's importance.

 

Lesson learned DO NOT THROW AWAY ANY OLD PARTS UNLESS YOU 110% KNOW YOU DO NOT NEED THEM. And still just hang onto them anyway. Did you remove the part in the pic? How is you rear axle brake T block staying in place?

Yes you need a vent for the exact reason earlier stated. Axle builds up pressure from operation, it has to vent somehow. Also needs to have a rubber hose on the vent pipe to keep water, road grim out. And a very simple filter keeps the mud daubers out of the end of the hose.