I do remember it seeming slow, but - compared to my pewter Horse - they all are! 😁
Here's the reason I swapped transaxles in your 522..... a really nasty right axle:
For those who are curious...... the layout of the innards of the xi tranz:
Input bevel gears, hi-lo cluster, and primary reduction shaft:
With the exception of the square vs. woodruff key, the axles appear to be the same as the "classic" 8 speed and Eaton hydro tranz 1.125" pieces.