I got a set of v6 diffs from marlin and was wondering if anyone knew what this hole is on the top that doesn't have anything in it (silver part in the photo, it is on the top of the diff)? I am assuming it is for a sensor, but I put the diffs in my 4cyl axles and the old ones didn't have anything like that on them.

Assuming it is for a sensor, I will then just plug it with a brass plug (unless there is another use or better suggestion). That brings me to the next question, what size / type are the threads on this thing? Kinda looks like 1/8 npt, but I'm not too sure. I want to go in to town tomorrow and pick up a few different things and oil so I can get these out on the road and broke in.

Here is a photo, the spot in the middle of the red dots.

 

I would guess it is for the vent .

It could be quite interesting if you plug it.

 

The vent is on top of the rear end.

 

Whoops! Didn't look closely enough at the pic. See posts below...

 

I believe on mine that hole you have circled is tapped for a M8x1.25 bolt, it holds the ABS sensor in the rear diff.

If you want to plug that hole I would personally make a block off plate out of Stainless or Alum and then use the provided bolt hole with a touch of red RTV.

cheers

 

So it looks to me that it is already blocked off and the threaded bolt hole is all that is left, if so you should be fine running it that way.

 

Yes, it is just the threaded part. The other part came with the metal "cap", which I would assume would be fine if left like that.

It definitely was not a 1/8 npt. lol. Bought a couple of them and no go. Took them back in looks for something smaller. Now back to the hardware store again to get a bolt.