Is it necessary to replace the front axle when replacing the transfer case?

What is your question?

I'm probably going to have to have the transfer case replaced in my 2006 Jeep Commander(not V8) and I've been told by a couple of mechanics that I should replace the front axle because it can get contaminated when they remove it to replace the case. What would they mean by "contaminated" and in your opinion, is it necessary to replace the axle? I know you have the remanufactured transfer cases but I'm not making any hasty decisions on this problem because it is an expensive repair and we have another vehicle to drive.

What makes this problem better or worse?

clunking noise on take off & once when going down a steep hill it sound like a chain slipped

How long has your 2006 Jeep Commander had this problem?

2 mos. for sure