So the current theory on why I keep munching B series input shafts has something to do with 4 cylinder diesel harmonics (?).. driving it under 2000rpm, eg: lugging it around at low RPM, and the 3.7 Ring and Pinions. I did notice a bit of a grating/grumble when driving under 1800-2000rpm on the 3.7's but didnt think much of it.. If anyone has any resources to help explain this theory or 4 cylinder diesel harmonics, I'd love to learn more.
When I put a Cummins 4bt (with a NV4500 5 speed trans) in a fj60 years ago, I took that transmission apart 3 times before I figured out that the hammering noise at idle was from the harmonics of the motor... The last time I took it to a transmission shop in southern Minnesota and they put it on there machine and ran the clutch and trans through its paces, it was nice and quiet, and they told me about the harmonics. It was a very frustrating and expensive lesson. Sorry, not much for tech, but I can relate.