So after spending an hour to squeeze a stacked washer/dryer combo into our basement (damn you, low stairwell ceilings), I realize that the dryer has a 4-prong plug, but the receptacle on the wall is an older 3-prong plug!

However, after opening up the receptacle box I find 4 wires:

I used my voltage meter to find the following readings:
Red-black: 240v
Red-white: 120v
Black-white: 120v
Red-bare: 120v
Black-bare: 120v
Here's the junction box side of the conduit (the thick white one in the back, with bare/red/black/white wires coming out of it):



So here's the question - this looks like a proper 4-wire 30-amp hookup, right? It's the receptacle that's old? Would it be a good idea/legal to replace the receptacle myself, since I'm not going to be running any wires? It appears to be a simple "unscrew wire" - "screw in wire" job. I should mention that I'm pretty handy with a drill and screwdriver. Just don't want to do anything that's not up to code.

However, after opening up the receptacle box I find 4 wires:

I used my voltage meter to find the following readings:
Red-black: 240v
Red-white: 120v
Black-white: 120v
Red-bare: 120v
Black-bare: 120v
Here's the junction box side of the conduit (the thick white one in the back, with bare/red/black/white wires coming out of it):



So here's the question - this looks like a proper 4-wire 30-amp hookup, right? It's the receptacle that's old? Would it be a good idea/legal to replace the receptacle myself, since I'm not going to be running any wires? It appears to be a simple "unscrew wire" - "screw in wire" job. I should mention that I'm pretty handy with a drill and screwdriver. Just don't want to do anything that's not up to code.