1998 4 Wheel Drive Problems

I have a 1998 Envoy that 2 weeks ago the 4 wheel drive "went". When I tried to switch on the fly nothing, when I stop and put it into neutral then press 4 Hi the 4 Hi and 4 Lo lights just flash but no change over. When I try just 4 Lo while stopped and in neutral then it goes right into 4 Lo no problem and it goes back to 2 WD no problem. I had one transmission place tell me it is the transfer case motor and two other places tell me it is the switch on the dash. The two other places tell me the switch in the 98 models had "faulty" solder joints and need to be replaced with a newer model from the factory. I would appreciate if I could get some opinions from people that have a pretty good idea what is wrong. :banghead:

Thanks!!