transfer case not fully disengaging the front wheels?

[timcrow00]

i got a 93 k2500 5.7, after goin from 4wheel to 2 wheel sometimes if i try and take off fast there is a loud banging come from what sounds like the transfer case. i would understand if it just took a little while to disengage but sometimes it will do it after days of no 4 wheel drive though not as bad. it started suddenly after i change my front drive shaft out with one i got from a salvage yard. and did some work in the front diff. could something i did doin that be causing my problems