The common consensus I found when searching prior to my build was that you were pretty well safe up to 35" with a stock D44. Any higher and you really ought to be thinking about alloy shafts. As was mentioned, fondness for the skinny pedal and driving style are major factors in the tire range you are talking for that axle.
Dana 44s never did cut it for my 4 liter YJ. I'm an old man and my foot is not heavy. Even the 35" Walmart tires took out the front u-joint, stub, and outer. On another occasion my left rear shaft broke at the end of the splines. You might do ok in mud and sand, but if I were upgrading to 38s, I'd be looking for axles that would have 35 splines. And a bigger ring and pinion that didn't deflect.:shaking:
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!