Speedo drive gear demolished!

Th
Hey guys, I need a little more help. I ordered a new drive gear, I put it in, and clocked it correctly based on the image above and the other research I've done. I took the car 5 miles down the road and it ate the teeth up again. The speedometer didn't bounce, there was no sign of it not working correctly. I have no idea what I need to do to stop this from happening again. I never had an issue until I had the transmission rebuilt.
they shimmed the trans wrong, go *****!