13mm square socket for Subaru rear differential

**mattthemuppet** · Nov 26, 2016, 07:07 PM

made a 13mm square socket from a piece of 1in hex to change the rear diff oil in my Subaru. Glad I did too, foul black stuff came out. Did the front as well (not quite as disgusting) and the CVT is next weekend.

used my lathe to face both ends of the hex (one from the scrap yard, one from me hacksawing the chunk off), then cut a groove to the diagonal distance across the hex (18mm?). Hacksawed off the corners and squared things up on my "mill". Worked a treat!

**Imabass** · Nov 28, 2016, 04:51 PM

Nice work but I have a question. Would a standard 1/2 ratchet or extension not work on the 13mm plug?

**mattthemuppet** · Nov 28, 2016, 06:02 PM

thanks and yes, a 1/2in ratchet or extension would probably have worked fine - others have done just that. I wanted to use that piece of hex stock for something useful and I was also worried about wallowing out one of the plugs, as it has a much shallower bore than the other one (5mm vs. ~11mm). They took quite a bit of force to get off too!

**DIYer** · Dec 1, 2016, 08:32 AM

Thanks mattthemuppet! We've added your Differential Square Socket to our Automotive category,
as well as to your builder page: mattthemuppet's Homemade Tools. Your receipt:

Differential Square Socket by mattthemuppet

tags: specialty socket

**richardinnz** · Dec 3, 2016, 06:12 AM

A 1/2" square drive ratchet will work.........until you get a tight plug. The square on the 1/2" ratchet will then shear off where the locating ball is because the square in the drain/filler plugs is not as deep as the square drive in a socket. I have 1/2, 3/8, and 10mm plug sockets which I use for work. Well done for making that.

**mattthemuppet** · Dec 4, 2016, 02:41 PM

funny you say that, I was trying to get the CVT fill plug out and the only 10mm male socket I had was a 1/4in drive and I don't have a 1/4in breaker bar. Fitted a 3/8>1/4 adapter so I could use my 3/8in bar and the bar started turning without the socket moving. This sent me into "alarm, rounding plug mode", firing up the MAP torch and freeze spray to shock it loose. Tried again and the same problem, but when I looked closely I realised that the male 1/4in part of the adapter was slowly shearing off.

got out my 10mm allen key and a piece of pipe to fit over it for extra leverage and it came off with the 1st tug!