4 wheel drive sounds strange on my 2004 ford ranger

Some noise is common, but excess play in the C-V shaft in the front drive units can caused excess noise. This is kind of a judgement thing; someone should put the truck on a lift and physically inspect the front components.

The splines on the drive shaft are probably worn down. See junk yard or dealer for replacemwent.

if its a 4wd then it could be the transfer case going out. check to make sure its in either auto or 2 hi. also check all you're fluid levels and drive shaft.

well you should not be engaging your 4wheel drive while truck is moving is my guess...doing major gear damage

you could have a worn wheel bearing or differential bearings

4L only to be used in extreme condtions
N
4H for off road/snow/ice
2H - normal driving

when switching to 4H vehicle must be stationary, as when changing from 4H to 4L
but it is possible to change from 4H back to 2H while in motion.
when 4wd is engaged a lamp will illuminate on dials telling that the hubs are free wheeling, when changing back to 2H you must press corresponding switch to dis-engage this function

tap on the 4wd motor on the transfer case while someone is pushing the button, if engages you need a new motor

It sounds like the electric motor for the 4 wheel drive may not be engaging. It could also be the magnetic clutch for the 4 wheel drive may not be working. This sounds like an electrical problem.

You pretty much answered yourself here, the switch sounds like it is going bad.

Its most likely either or, if its a high pitched sound its probably the wheel bearing. If its a growling/grinding/clunking sound its probably the CV Joint. However, your problem more than likely lies in either/both.