Outer Limits 4x4 Board

hi all i have not long ago fully rebuilt a 5speed h55 gearbox and mounted a later model 1988 larger layshalft model transfer case to it i had to replace the main drive gear with a new one with the longer spline, and also change the main rear transfer output shalft to a hj47 model shafts for the handbrake, all replaciple sincro's where replaced but i have a wine that starts in second and goes till 4th ,5th is ok i am running normal 80/90weight oil and wonder if changing this would make a difference i am willing to try anything as i dont want to have to pull it all apart again.

thanks Shane Mulcahy

the gearbox is in my hj47 and is out of a 1986 troop carrier and transfer off a 1988 75series ute