I'm looking for a transmission/transfer case combo for a 4x4 conversion. I've come across a good deal on a AW4/231 combo at a JY for a good price. The problem is it is from a 1988 so it's got a 21 input shaft.

I'll be putting it behind a stock 1991 4.0L.

Is there a big strength difference in the 23 vs 21 spline. The 23 spline combos I've found are 2x the price or more. I have no problem putting a slightly weaker combo in but I do have a problem putting a combo that will leave me wondering if it'll leave me stranded.