I have an 83 ish cab truck with the 22r on propane and 36's and stock everything else. I plan on new 5.71 ring and pinion with 4.7:1 t case twin stick kit. I was just wondering how big a tier I could run before it'll snap stock axel shafts. I also plan on hydro stear and cromeolly shafts as well. Thanks for the input and advice

 

Do some searching on the 5.71 gear set. The word on pirate is they are weaker than the 5.29 set. with the 4.7 case you won't need the extra gearing of the 5.71s. Generally speaking, factory axle shafts are good to a 36" tire and a factory 4cyl, depending on how you drive. Smaller if you have more torque (such as your 4.7 reduction) It will be your birfields that pop first, but if you're careful with the skinny pedal and keep your tires as straight as possible they will last longer.