I always make sure my 06' 1500 4x4 is in neutral
even if it doesn't have to be. Usually the flashing
light means it's going into 4x4, when the light stops
blinking you should be in 4wheel drivs. I believe
(could be wrong) that you must let it lock in 4lo
before switching to 4hi. But if the light doesn't stop
blinking then it's not in 4 wheel drive.
I've never personally heard a noise when mine is
switching over I just know you must run your
vehicle in 4 wheel drive every so often in order to
keep all the parts working properly and lubricated.
So maybe the previous owners didn't do this.
Probably not a lot of help here but if you wanted a
little insight I hope I did something lol.