Long story short, the installer who put it in (1.5 years ago) didn't shim it properly, the ring gear/carrier was walking a smidge. Over the last year, it was wearing on the bearings bad, to the point where the pinion finally started pulling the ring gear closer and closer, rocking it back and forth. It all ended when it had finally pulled the carrier close enough to start wearing on the toe side of the ring gear to the point where the teeth started busting off. I'm not sure if the pinion teeth busted off first and started gouging the ring gear or vice versa but you can see the outcome.
Suprisingly, the truck was still driving forward without slack or slippage, just vibrations. It all started on Tuesday with a very very slight hum, thought it was a wheel bearing. Wednesday morning it was worse, with a mild vibration on accel over 55 mph, none on decel. By the end of the day, the vibe was getting a little louder and more pronounced earlier in the speed, like 45. By now, I was 99% sure it was a pinion bearing, would've bet money on it. Thursday morning, the vibe was horrible, like the truck was riding on 4 seperated tires. Couldn't hardly get to 35 and it sounded like the whole rear end was gonna blow. Drove it maybe 3 miles to the office and parked it. Just way way too bad to drive, I knew it was something major. Picked it up with the trailer that afternoon and took it to my bud's house where we quickly tore into it to find busted ring gear teeth and gouges on the carrier. Had it the whole rear end emptied in about 30 min. UPS overnighted a new ring/pinion and rebuild kit from Randy's and had it first thing Friday to begin the install.
There's no way the carrier shims that were in it were correct, there wasn't near enough in there and the few shims in it just fell out and were majorly loose. With this axle, when you have it all shimmed right and are ready for a wear check, you add a .006 shim to each side to load the carrier bearings and there wasn't anything in there to load those. However, it went back together perfectly and actually in one try, surprising with our limited tools. We checked and double checked and the lash was dead on after we were done and the pinion depth was ideal. So, now it's just break-in.
