2003 Discovery

I started to remove the front differential plastic fill plug in order to replace the leaky seal, but soon realized the plug was continually spinning and not coming out, even though the plug was past the threats. I eventually pulled it out successfully. I thought this to be strange, but figured I had somehow damaged the plug the last time I installed it.

I purchased bronze fill plugs and put no more thought into it until I received the bronze plugs and attempted to install them. Very soon after attempting to install the plugs, I noticed it became unusually difficult to spin, despite the threads being properly aligned. I removed the plug and looked inside the differential fill hole with a flashlight and noticed a small metal obstruction, similar to a metal glob caused from welding splatter, on the inside of the differential wall, partially blocking the hole and thus preventing the plug from inserting. I pulled on it with my finger, to no avail. I tapped on it with a screwdriver, again to no avail.

I have no idea what it could be or how it got there. Any ideas? My plan is to run a tap through the fill hole to clean out the obstruction. Any better ideas? Anybody know what size tap I should purchase?
Thanks.

 

Well if you run a tap through you will need to have a bunch of cheap oil handy to fill rotate by hand drain and filter and repeat a bunch of times. If it was me I would open it up and see what is actually going on

 

Can you get a good picture through the hole to show us what you're seeing?

 

First what type of Tap will you use a starter tap,I would pack the tap with grease to try and prevent the metal piece from dropping inside, be aware that it the spatter is fast it may break the tap,
lastly have you measured the depth of thread you have and if so is it possible to cut down the new plug so it will go in with out removing the offending bit of spatter

 

 

The gears inside look normal. I have no clue how this metal glob got there. It's very small, but hard enough to not remain in place after a few mild strikes with a hammer and screwdriver.

 

Old thread maybe from a cross threaded filler plug, but very odd

 

The original plug that I removed is plastic. I don't see how the plastic plug could damage metal threads.

 

@HopeItsNotAMoneyPit I was thinking a PO used a metal plug and screwed it up then used a plastic one to make do

 

Have you tried removing the most of the metal with a file or a Dremel tool then retaping it