After The Fire's cover of Der Kommissar made it to #5 on the pop chart. The original by Falco made it to #74 on Cashbox, though it had much better success on the Dance Club (#10) and Mainstream Rock (#22) charts.
Interestingly enough, the Falco original and ATF cover peaked in the same week in January 1983 on the Canadian pop chart at #11 and #12, respectively.
Dallas Fraizer first recorded "Elvira" in 1968 but it only got to #72 on Billboard's Hot 100 chart, the Oak Ridge Boys covered it in 1981 and took to #1 country and #5 Billboard Hot 100.
And if you use R&R Casey's Top 40/Rick Dees sources, in Summer 1994 (as the old AT40 was on its deathbed that time) Frente made the R&R CHR/Pop top 40 with "Bizarre Love Triangle", a nearly 2 minute cover version of a 1986 song by New Order which never made Billboard's Hot 100.
Here's one from the Shadoe AT40 era: In 1990 there was the #1 song by New Kids on the Block called "Step By Step" which was a remake of a song in 1987 done by the Dynamite Superiors - That Superiors version never made Billboard's Hot 100.
^Except the original is by the Persuaders and it did hit the top 40, barely, in 1973.
Just in case anyone else doesn't recall this thread from back in 2015/16. The Persuaders' original is head and shoulders above EITHER remake, Palmer or Stewart. It's a superb slice of early '70s soul. #39, December 1973.
Listening to the 6/6/92 AT 40 show made me realize one I that should have come to my mind earlier: "Wishing On A Star" by The Cover Girls was on its way into the top 10 in the summer of 1992. The original, done by Rose Royce in 1978, failed to hit the Hot 100.