turbo problems

[Heepdriver]

i am triing to put a 16cm exhaust housing on a 91 ctd, the exhaust side went on no problem but while putting the intake side back together, i ran into a problem. when i tighten the nut for the compressor wheel the wheel wants to catch as i am triing to turn it. if i loosen the wheel up it will turn freely. i know its not a housing clearance issue but it seams like a bearing is catching or it is too tight. there is no play in the shaft and it did not do this when i took it apart. if you have any suggestions let me know.