Any reason for the lip on the differential fill plug?

[Hatsuwr]

Part 9034118032 I believe.

I have some extra high-temp neodymium magnets, and I was thinking about putting one on my differential fill plugs to see if they have much effect. Obviously wouldn't be as useful as on the drain plug, but it can be inspected and cleaned without draining the oil.

I figured I'd drill a hole a few mm deep to help retain the magnet, but that would have the face of the magnet recessed below the lip on the plug. Does that feature serve any purpose?

It seems unlikely it would be there if there wasn't a purpose. It almost seem like it may have actually been for a magnet originally. There are similar plugs with magnets, although they are intended as drain plugs and definitely don't have that prominent lip. One example is the 9034118021:

 

[2001LC]

Possibly, it is a drain plug with magnet, in some other vehicle.

 

[Hatsuwr]

Possibly, it is a drain plug with magnet, in some other vehicle.

Seems most likely, although I'd be surprised they'd leave that out on the LC/LX. Unless maybe the part was originally used as a drain plug and they removed the magnet to use it for a fill plug.

 

[Dirt J]

Personally, I would NOT attach a magnet to a fill or drain plug myself for fear it would come "unglued" and mess something up inside the diff or tcase.

I used the factory magnet plugs you mentioned (90341-18021) to replace the ones in my rear diff. This a common mod to prevent dealing with a damaged hex head drain plug. Did the same for my tcase too I believe.

 

[Hatsuwr]

Personally, I would NOT attach a magnet to a fill or drain plug myself for fear it would come "unglued" and mess something up inside the diff or tcase.

I used the factory magnet plugs you mentioned (90341-18021) to replace the ones in my rear diff. This a common mod to prevent dealing with a damaged hex head drain plug. Did the same for my tcase too I believe.

That's definitely concern! And the factory ones are my backup.

My main reason for wanting to DIY it was so that I could use high temp neodymium magnets. The plan is to use an end mill to get a precise hole with a flat base, then in the center drill a small hole through to the outside of the plug for excess adhesive to exit through. Then use something like JB Weld when installing the magnet for some backup holding power. Finally I was thinking about taking a punch to the perimeter of the plug around the magnet, with the hope of deforming the hole slightly to give it a bit of an interference fit.

Did you find that your magnet in the fill plug actually captured much?

 

[Dirt J]

Yes, it does. Ideally it catches "mush" or "paste". Finely ground up metal (from the gears, I suppose). I can't recall changing gear oil on any vehicle I've ever had and NOT finding some amount of paste on the magnet.

Hunks are sign of a problem!

EDIT: Sorry! You were asking specifically about the FILL plug. I can't say for that. Not sure I've changed the fluids since that mod.

 

[Hatsuwr]

Yes, it does. Ideally it catches "mush" or "paste". Finely ground up metal (from the gears, I suppose). I can't recall changing gear oil on any vehicle I've ever had and NOT finding some amount of paste on the magnet.

Hunks are sign of a problem!

EDIT: Sorry! You were asking specifically about the FILL plug. I can't say for that. Not sure I've changed the fluids since that mod.

Yup drain plug magnet is vital in my opinion. I'm guessing that the fluid will be thrown around enough that the fill plug one will be useful too, and if so it has the benefit of being able to clean and inspect it without draining.