I've got a 10 bolt 8.5" rear end with bolt in axles going into my '70 Cutlass and I'm just bolting up the backing plates and bearing covers. Should there be a gasket between the backing plate and the axle housing? I have one (part is labelled for 64-68 Cutlass though) but couldn't find reference to anything in the assembly manuals. If the gasket is used, does it go on dry or with some goop?

Also, any tricks to getting the outer seal started into the housing?

 

There was a gasket originally. You can also just use RTV.

 

I have swapped quite a few rearends in my car and never saw a gasket on the backing plate. I suppose it’s a dust seal?

 

Yes, that's exactly what it is, dust and water seal.

 

It's not much of a gasket, more like a piece of paper. I'll reuse it if it is still intact, but I won't replace a missing one.