  We analyzed the 3-mm wavelength spectral line survey of 408 ATLASGAL clumps
observed with the IRAM 30m-telescope, focusing on the class I methanol masers
with frequencies near 84, 95 and 104.3 GHz. We detect narrow, maser-like
features towards 54, 100 and 4 sources in the maser lines near 84, 95 and 104.3
GHz, respectively. Among them, fifty 84 GHz masers, twenty nine 95 GHz masers
and four rare 104.3 GHz masers are new discoveries. The new detections increase
the number of known 104.3 GHz masers from 5 to 9. The 95 GHz class I methanol
maser is generally stronger than the 84 GHz maser counterpart. We find 9
sources showing class I methanol masers but no SiO emission, indicating that
class I methanol masers might be the only signpost of protostellar outflow
activity in extremely embedded objects at the earliest evolutionary stage.
Class I methanol masers that are associated with sources that show SiO line
wings are more numerous and stronger than those without such wings. The total
integrated intensity of class I methanol masers is well correlated with the
integrated intensity and velocity coverage of the SiO (2--1) emission. The
properties of class I methanol masers are positively correlated with the
bolometric luminosity, clump mass, peak H$_2$ column density of their
associated clumps but uncorrelated with the luminosity-to-mass ratio, dust
temperature, and mean H$_2$ volume density. We suggest that the properties of
class I masers are related to shocks traced by SiO. Based on our observations,
we conclude that class I methanol masers at 84 and 95 GHz can trace a similar
evolutionary stage as H$_2$O maser, and appear prior to 6.7 and 12.2 GHz
methanol and OH masers. Despite their small number, the 104.3 GHz class I
masers appear to trace a short and more evolved stage compared to the other
class I masers. [abridged]
