3.09 4 Speed Gear Set Strength

The weakest gear on ANY 833 is 3rd. So it’s true. The 3.09 box is no weaker than any other 833.

That's for sure. I had an A833 converted to a crash-box setup and before long it stripped all the teeth off third gear during a quarter-mile power shift with a built 273. Surprised the heck out of me at the time (I used both 3.09 and 2.66 first gears in the vehicle-the close ratio was better with the 4.56 rear end I was using).