Magnet

[Mrkentee]

I recently replaced my rear drive axle housing with a new one. And I hate to admit it, but I forgot to put the magnet in. This new one does not have a drain plug on the bottom. They tell you to take the lower bolt out of the differential, and drain it that way. I put the same oil back in because it wasn’t too old. I’m thinking I’ll wait till I change the oil again, and then pull that differential out a ways and put the magnet in there. Does that sound reasonable?

[Yauchout]

My meritor axle had three magnets in it. I'm not sure if you removed all of them or not. Another brand may have less or none. That being said, you could get on Amazon and buy large neodymium magnet and stick it on the outside in the meantime, probably wouldn't perform as well as one inside the oil, but it would still catch some iron

[Pigpen 2869]

Use a magnetic fill plug.

[Nostalgic]

It's a little late now and kind of a rough job to do upside down, but I drilled and tapped my new housings for a drain plug before I put installed them. I thought it was pretty stupid for them to cut costs by having you take out a bolt to drain - you can't peek in with a light or stick your finger in to feel for chunks or bigger shavings, and the bolt you remove to drain isn't all the way at the bottom anyway if I remember correctly.

Magnetic fill plug can grab enough to let you know general health, but if there's bigger chunks pre-failure, it might not catch them.