I have them both on the bench with no visible damage to either one...... The axle shafts new and old are close to being the same length (nitro axles are .25 shorter in length) and the Nitro axles also have a shorter splined section, maybe 2 inches long where as the factory ones have a spline section that is 3 inches or so .

With the diffs on the bench they appear to function as intended. Good pinon engagement and no damage.

is it possible the axles are not engaging both sets of splines on the left/right side? I can see some engagement when I pull the shafts. They appear to engage about an inch.

Thank you