Carrier bearing problem lowered truck !

[BCOWANWHEELS]

Guys i have a problem ! I have a 72 lwb chevy tk., its been lowered 5" front and 7" rear as low as you can go with springs only. Anyway about every 10k miles i broke a drive shaft carrier bearing in the long section between the top of the bearing and where it mounts. I have no vibrations when driving and it turns freely when up on jack stands. I have all new u-joints and the carrier bearing assy is national brand, u-joints are timken and i grease them every 2k miles. My engine is a stock 350 with a th350 turbo trans. I,am a old fella so i drive very reasonable not doing burnouts or hard starts. AnY help or tips on this matter will be greatly appreciated.
Regards
bob in tn.

P/s
i will post a picture of the broken carrier bearing latter today when i get it off. Sorry about the caps i have bad eyes & hard to see small type !