I have a 1984 Ford F-150 4x4 and I am having trouble removing the rear differential fill plug. The fill plug is really rusty and there is almost nothing left of the square hole in the center I tried turning it out and the 3/8 drive extention wants to slip in the hole. What would be the best way to try to remove the plug?

 

Start by soaking the plug with WD-40 two or three times a day. If that doesn't work after like two days, you may have to weld a bar onto it so you can grip it. Hopefully somebody will have a less drastic approach, but it's late and that's all I can think of.

 

well you may have to weld a piece of rebar in the hole and take it out that way.

 

I'm thinking about putting a bolt in the hole of the plug and welding it to the plug. Then trying to turn the plug out with the bolt. The heat from welding it should also help break the plug loose. I know I have to watch how hot I get the differential housing because of the seals and the fluid in it, but I think this will work. What do you think?

 

The heat from welding it will cause the plug to enlarge, so try to keep it to a minimum. If you just tack a bar across the plug you won't have to worry about grabbing the bolt and twisting the welds off the shaft of the bolt. You want your tacks to be close to the edge to give your more torque on the plug and less force on the welds.

 

I have been able to get those plugs out if there is a little bit of the plug sticking out of the case. I just use a cold chisel and a hammer and whack it a couple times along the top edge of the plug, usually this is enough to break the rust free. Next time I have to take my plug out I'm going to replace it with a pipe plug with the square on the outside.

 

Watch out for rocks and curbs.

 

Not worried my fill plug is on the side of the diff housing up and out of the way, it's an 8.8. BTW try PB Blaster or Deep Creep on that rust, both will power through it better than WD40.

 

You and your fancy tricks.

 

if you have a sand blaster give it a quick blast. Works wonders to clean up any rust and crap inside the plug