Diff drain plug. Odd size.

[keithb7]

Hi folks. I went to drip my diff oil recently to service it. The drain plug   Has a flat surface with an inset square drive. Normally I’d insert a ratchet in the plug to loosen or tighten it. 

I have ¼, ⅜, ½, ¾ drive ratchets. None fit it. Seems weird to me. Is there a special tool with an odd square drive to fit this drain plug?  I’ve never come across this issue before in my life. But hey, this is my first car built before 1968.

Maybe I best get some square stock and a file and get to grunting  

Thx. 

Edited October 23, 2017 by keithb7

[Young Ed]

Yes there are sockets that go in those odd ball inbetween sizes. I believe some guys get square stock to fit and then use an an adjustable wrench on the stock. 

[plymjim]

Also, at one time you could get a wrench, I called them a dogbone.

About 10" long with several different size square nubs on each end.

Maybe another forum member remembers the tech. name. Might still

be available somewhere.

[Merle Coggins]

As I recall it's a 5/16" square. The first time I ran into it I found a punch in my tool box that had a body with the same size square. I inserted the square side into the plug and used a wrench on the square shank of the punch. Then I found a socket set that has the male square ends for this exact purpose.

Here's a set on Amazon with both internal and external square sockets. https://www.amazon.com/SK-19781-Piece-8-Inch-Socket/dp/B0002NYC7C/ref=sr_1_22?ie=UTF8&qid=1508790783&sr=8-22&keywords=square+plug+socket

Another similar set on Tooltopia, a bit cheaper. https://www.tooltopia.com/grey-pneumatic-1211p.aspx?utm_source=google&utm_medium=cpc&utm_campaign=paid_search_google_pla&adpos=1o8&scid=scplpGRE1211P&sc_intid=GRE1211P&gclid=EAIaIQobChMI_PDKuMuH1wIVArjACh0AqwubEAYYCCABEgKjSfD_BwE

Edited October 23, 2017 by Merle Coggins

[Jerry Roberts]

55 minutes ago, plymjim said:

Also, at one time you could get a wrench, I called them a dogbone.

About 10" long with several different size square nubs on each end.

Maybe another forum member remembers the tech. name. Might still

be available somewhere.

I just saw two of these on ebay yesterday . I think that they were listed as drain plug wrenches , used , with a fair price . With a grinder it is easy to make the correct size from a bolt or stud , that is what I did .  

[Plymouthy Adams]

with the modern tools have a mixture of metric...be sure to use the phrase that pays...."vintage universal drain plug wrench"

[knuckleharley]

5 hours ago, keithb7 said:

Hi folks. I went to drip my diff oil recently to service it. The drain plug   Has a flat surface with an inset square drive. Normally I’d insert a ratchet in the plug to loosen or tighten it. 

I have ¼, ⅜, ½, ¾ drive ratchets. None fit it. Seems weird to me. Is there a special tool with an odd square drive to fit this drain plug?  I’ve never come across this issue before in my life. But hey, this is my first car built before 1968.

Maybe I best get some square stock and a file and get to grunting  

Thx. 

A quick "fix" that will enable you to get the plug out where it's easier to see what you are doing and work with it is to take a socket extension slightly smaller than the fitting,cover the end where the plug goes with a shop rag,and then take a hammer and gently,or not so gently,tap the extension into place so you can remove the plug.

Who knows,you might be able to find one the same size at a big hardware store that DOES fit US square drives,and save yourself a bunch of work and a ruined extension?

[_shel_ny]

A short piece of 5/16" square stock worked fine for mine.   Remove once. Install once. No special tool purchase/fabrication needed.

Of course any excuse to buy a new tool is a good reason to get one.

[Dodgeb4ya]

5/16".............. easy.

[Niel Hoback]

I think it's the same size as the rear axle hub key.

[dpollo]

I have always used a door handle or a trunk latch.  The shaft fits very well.

[Worden18]

I had the same problem earlier this summer, Keith.  I had my car up on a friend's hoist.  He took a look at it and happened to have a piece of 5/16 square stock amongst all of the excess things piled up by his drill press.  Slapped on an adjustable wrench and finished the job.