Totally understand Ed, but its the acceleration where the issue is occurring not the downshift. As I split shift up, the axle refuses to shift up from 3 hi and into 4 lo. I know certain setups have very particular shift patterns, but this setup, as per dash and manual instruction, is 1 lo - hi, 2 lo - hi, 3 lo - hi, 4 lo - hi and it is that jump from 3 hi to 4 lo where it simply grinds away.
Hypothesis is that something was installed improper, but again, it is only this junction that does it, and theoretically if something in the diff was wonky, it would do this at all 3 shift jumps (1 hi - 2 lo, 2 hi-3 lo, 3 hi - 4 lo) but it only does it at the latter.
