I would like some advice on how to install the new roll pin into the speedometer cog housing.  I pulled the old pin out with pliers and vice grips, but that method "boogerd up" the pin pretty badly.  The new roll pin (which is the correct Nissan replacement part) seems slightly larger in diameter than the hole in the housing.  I'm guessing this is the way it is designed to be.  Because the housing is oddly shaped and made from soft metal (aluminum?) I'm hesitant to clamp it too tightly in a vice.  So, practically speaking, what is the easiest way to drive this new pin into the housing without damaging the pin or the housing?

I would start it from the left side. Lay the back edge on a block of wood and tap it in. Add a little oil to help. Shouldn't need much encouragement

Using a block of wood is a good idea.  I've messed around with removing and replacing those pins and they are difficult.  You can build a little holding jig, two blocks of wood next to each other, to sit the piece in the groove between, to keep it from rolling.

Filing the end of the pin down to a sharper point to give it a better start helps also.  The end of the pin doesn't matter once it's installed.

Thanks for all the good advice.  Time to get to work on it.  I'll let you know how it went/what worked for me when I'm done.

 

OK...I got the pin installed.

I think the key to this task is first to get the cog housing solidly fixed so that it doesn't move any at all when you're trying to drive in the roll pin.  I built a "jig" from a couple scraps of wood and this worked nicely.  I also figured out a way to get the housing solidly fixed into a vice so that it wouldn't move while driving in the roll pin.

Also, to get the roll pin started, I filed one end of it down enough so that the pin started into the hole enough to make the first few taps with the hammer easy.

Thanks again for the advice....now on to the next problem!