[kevingross]

Probably dog teeth, a little hard to be completely certain from the angle of the bits in the photo. One definitely looks like a dog tooth.

Let me offer you, at no cost!, some advice. First, given that you have debris inside the transmission, it needs to be thoroughly disassembled, cleaned, and inspected. Debris gets into everything and everywhere, and a quick fix is not in your long term best interests. If you're lucky enough to have an LSD, they are fantastic at somehow ingesting debris and galling their clutch discs, for example.

Second bit of advice is that until the transmission is opened and inspected, you really have no idea what it's going to cost to rebuild. Two reasons for this: you cannot know what has been damaged by the debris, and unless someone has rebuilt your transmission in known history, you have no idea of what else needs attention. That broken dog ring is unlikely to be the only old, tired part needing attention.

Third is that the hassle of crating and shipping your transmission is very small compared to the migraine of dealing with a repair done improperly. I don't know Rennsport KC but if they've done a bunch of 915 gearboxes, have the special tools and know-how, it's worth the drive. If not, CMS does great work -- so do I (shameless plug, sue me!). What I do for my customers is arrange pick-up with an LTL freight carrier; all you have to do is get the transmission safely crated or lashed to a generic pallet.

Good luck with the project!