2nd Gen Non-Engine/Transmission front axle noise

[98slushbox]

I have a factory front end in my 98. When i lock it in 4 wheel drive and begin to drive there is a popping in the front axle. I tore it apart a week ago and found that on the passenger side of the differential the collar that connects the two right axles was slipping on the intermediate(or the axle shaft closest to the differ. ) so i replaced the interm. axle, seals and bearings. I got it all back together and the same problem occurs. I think what is happening is the interm. shaft is sliding away from the collar and outer shaft into the spider gears. I was wondering if there is something designated to hold the interm. shaft in, because there wasn't anything on mine. please respond if you can help