how to move x labels to be over facet labels in ggplot in R

Question

I would like to move the facet labels (3, 4, 5) to underneath the x values (4, 6, 8). My current code:

library(ggplot2)
ggplot(mtcars) + aes(factor(cyl), wt) + 
geom_bar(stat = "summary", fun.y = "mean") + 
facet_grid(~gear, switch = "x")

currently, it looks like this:

I'm looking for something that looks like this:

Answer 1

library(ggplot2)
ggplot(mtcars) + aes(factor(cyl), wt) + 
geom_bar(stat = "summary", fun.y = "mean") + 
facet_grid(~gear, switch = "x") +
theme(strip.placement = "outside")