Outer Limits 4x4 Board

I'm having trouble getting the new pinion seal in my rear diff. It looks like the right one, I bought it from Toyota, they checked all sorts of numbers before they gave it to me but the bugger want go in. Ive tried a few taps with a hammer and block of wood but I hit one side and the other side pops out.
I'd like to have it sorted within the hour so I can go to work this arvo.
Any ideas on how to get the bastard in?

The old one seams to be made of some kind of plastic, this one looks like copper.

PS. Yeah, I know this could go in Toyota but I figure you all got pinion seals and might have ideas.

They are a tight fit. You need something round, like a large socket, that fits over the pinion, and touches the seal around the edge. You put this against the seal squarely, and hammer it straight home. A piece of thick wood, with a hole in the centre would do the trick.

All sorted. I got off outers, went back to it, was there for about a minute and she was in like Flynn. Guess I just needed 5 mins break. Cheers for you're help mate.
all back together, tailshaft back on, oil in the diff and I'm off to work!