The collar can make it a nuisance to change the carrier bearing if everything doesn't cooperate. I'm pretty sure that the collar is 'permanently' attached to the propshaft. It makes it hard to change the carrier bearing under the truck if the carrier bearing is stubborn. A simple task becomes harder.
Last one I did required me to put the propshaft in my bench vice and very carefully remove the old carrier bearing using a combination of an angle grinder, Dremel cut-off wheel and a cold chisel. I had to cut the old carrier bearing off the shaft. It's trash anyway, but it was a pain to get off. Don't damage or cut the prop shaft or the collar. The new carrier bearing slid right one and reassembly was easy.
I'm not sure what the purpose of the collar is other than to be a dust and rain shield, but I figured that if GM put it there, it must be there for a reason.
Most old propshafts that I see in salvage yards have dented or mangled collars. You aren't the first one experiencing the joy!
Matt
