Rear differential drain plug

[Vaanth]

Trying to figure out the size of the rear differential drain plug on my 73’ 318 Auto charger. I believe it’s a Dana not exactly sure the size 8 1/4 maybe? I’ve tried a 3/4 square socket (to large) also tried 11/16 12 point socket almost grips but slips under tension a open ended 17 is not to large and a open ended 16 is to small. I attached some photos using a caliper it read ~.667”.

View attachment 1928676

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The pictured rear axle is an 8-1/4", built by Chrysler, not by Dana. The original fill plug is 5/8 inch (0.625 inch) across the flats. The pictured fill plug flats appear damaged. The shown caliper measurement of 0.667 is not directly on the flats.

A 5/8" open end wrench normally will fit the plug flats as shown in the following image:

If a wrench can no longer fit, or if the plug is too tight for the wrench, use a 5/8" square socket as the best choice to avoid further flat damage and to allow for a higher leverage tool. Other means can work, but can be riskier to the plug and more difficult to fit in place.

The plug used on the 1969 through late 1976 8-1/4" axle is the same as used on the 8-3/4" axle. In late 1976, the threaded filler plug for the 8-1/4" axle was relocated to a new cover using a rubber filler plug.

 

[j-c-c-62]

Based on your picture above you might want to get a new member name, may I suggest "Rear Ends R Us"?

 

[eldubb440]

 

[o1gnah]

Got it out by hammering a 6 point 5/8 socket while applying a torch! Now to find a replacement plug since it’s lodged in the socket and more than likely needs to be replaced. Thx

 

[Rishi]

Got it out by hammering a 6 point 5/8 socket while applying a torch! Now to find a replacement plug since it’s lodged in the socket and more than likely needs to be replaced. Thx

well done. any hardware store pipe-threaded plug may hold, until you find an OEM-looking one. As others have said, it doesn't need a great seal of torque to seal. You can hand thread your existing one back in there, and hammer off the socket to recover. PTFE tape works pretty well to seal against oil.