FWIW, and to clear any confusion, the axle spline count has nothing to do with the axle ratio.

4.0 with auto will be 3.55.

If you wanna be sure, there are tags on the diff covers, held by 2 bolts. For your use, don't worry about spline counts etc.

Okay, so any 4.0 auto axle will work. That’s good, I was worried about finding an axle with the same gear ratio because I would have no clue how to know the difference. Thank you so much!