Front driveshaft on a 98 ZR2

Can anybody tell me if it is normal for there to be play in the front driveshaft where it goes into the transfer case?I am getting a constant hum when driveing 55-60mph(2 wheel drive) and upon inspection I found that there is some play in the front driveshaft where it goes into the transfer case(the thing that looks like a cv joint),when pushing up and down.I just had the front wheel bearings done and the u joints are OK,so it's not them. :disappoin