In Reply to: oil pan plug posted by Kriss (ORE) on July 08, 2018 at 18:06:27:
FYI: ALL three large oil drain plug hex sizes AF (Across Flats) are 1-1/16" not 1-1/4" -could it be you're using the wrong size wrench? By the 'three' I mean the one furthest most forward for engine oil ( on the oil pan ) and the other two moving towards the diffy case which are for the hydraulic oil. The 3rd hydraulic drain plug is on the bottom of the diffy case. It is an NPT Pipe Plug with a 9/16" square head. It's been my experience when working on these old N's that one is usually the most difficult to remove mainly because it is often neglected or not known it is a drain plug. It maybe the PO torques the drain plug down with a heavy fence-post type breaker bar and didn't use a lubricant either. Some guys get oil leaks and think the solution is to crank down on the plug. If the plugs don't have gaskets, and the PO may have not installed a new gasket on the plug as well, leaks may occur. You won't know until you get it off. When doing oil changes, always take some clean, fresh oil; motor oil for oil pan plug, hydraulic oil for the other three plugs, and smear the entire new gasket both sides with oil. Also apply clean oil on the threads as well. Some guys like to use 'Anti-Seize', but use a very small amount. That'll make the next plug removal a bit easier. The original gaskets were cork and some new suppliers now use rubber and often both will dry rot on and make removal difficult. You can try using a good, 6-Point 1-1/16" socket, with a decent breaker bar to loosen stubborn plugs. I use this method and never had any not come off. When re-installing, only use the wrench and no breaker bar -they don't have to be THAT friggin' tight. NEVER use channel locks, vise grips, or pliers on fasteners. That is a sure way to muck up the hex and round them off. NEVER OVERTIGHTEN any fastener.