My range receptacle has two issues. Someone installed a four wire outlet, but only three wires to the receptacle. The wire is aluminum installed probably when house was built in 1980. Is this something I need to replace before I install a new ceiling in the basement?
It is working fine right now. It will cost less than $30 for the wire to fix it, but it will be a fair amount of time. Most of the time will be working behind the range. The range has both gas and electric and I don't want to disconnect gas to pull it out all the way.
Your range has both gas and electric?
Wow. Ive never seen that before.
If u switched the outlet to 3-prong 10-50 made sure the stove is setup as 3-wire(bonding strap from chassis to neutral terminal on terminal block) and changing cord to 3-wire obviously, it will be code compliant.
Where does the circuit originate from? Main service panel or subpanel?
Assuming you have a valve right at the range, I'd shutoff the gas, pull the range out, and give yourself clear and easy access to do the electrical job right. I am fairly OCD and would absolutely fix it before finishing the downstairs ceiling.
If I play internet archeologist, I'd wager that the house was originally built with a Nema 10-30 or similar (ungrounded 3 pole) and someone later "upgraded" that to a 4-pole outlet (14-30 or similar) and then either tied the neutral and ground together (code and safety violation) or left the ground unconnected (ditto).
"It's working fine right now" doesn't mean it's safe and proper. There is no safe way to provide all four connections (Line 1, Line 2, Neutral, and safety ground) over 3 wires.
10-30 and 14-30 is for dryers
10-50 and 14-50 is for ranges
A 3-wire connection is just as safe as a 4-wire as long as its installed properly. Many installations have the 3-wire branch circuit terminating in the main service panel so both neutral and ground land on the same neutral bar.
The potentially unsafe part has to do with the stove's chassis/ground being bonded to neutral which is required for 3-wire operation. If the neutral connection to the panel ever failed, then neutral return current can flow from the bonded chassis through someone touching it with one hand and touching say a metal water line or faucet with their other hand.