recently purchased 99 grand cherokee with with blown motor and replaced with remanufactured. engine sounds great, however, at about 40 mph when applying throttle, i hear a faint hum/whine. front dif fluid and gasket has been changed, replaced trans filter and fluid. transfer case rear retainer gasket is leaking but fluid is still at upper fill hole. hoping for advice on how to move forward. thanks

What about rear diff and axle bearings and components?

Thanks for the response, i have not checked those items yet. Will do this week.

update: checked rear dif, front bearings and and cv. seem to be functioning properly. i was thinking bearings in the front dif but my brother thought transfer case. removed front drive shaft and noise is gone. thoughts?