A downhole tool for use in a downhole drill string, the downhole tool comprising: a drive shaft (1436, 1836, 1936) movably coupled within a bearing housing (1444, 1844, 1944), wherein the drive shaft (1436, 1836, 1936) has a first end and a second end; a rotor coupled with the second end of the drive shaft (1436, 1836, 1936); a stator coupled with the rotor; and a bearing assembly interfacing engagement between the drive shaft (1436, 1836, 1936) and the bearing housing (1444, 1844, 1944), the bearing assembly comprising: a plurality of spaced-apart polycrystalline diamond elements (1501, 1801, 1901), wherein each polycrystalline diamond elements (1501, 1801, 1901) has an engagement surface (1513, 1813); and an opposing engagement surface (1515, 1556, 1815) comprising a metal, the metal comprising at least 2 wt.% of a diamond catalyst or diamond solvent based on a total weight of the metal, wherein the opposing engagement surface (1515, 1556, 1815) is movably engaged with each of the engagement surfaces (1513, 1813); wherein the plurality of polycrystalline diamond elements (1501, 1801) are coupled with the drive shaft (1436, 1836) and the opposing engagement surface is a surface on the bearing housing (1444, 1844), or wherein the plurality of polycrystalline diamond elements (1501, 1801, 1901) are coupled with the bearing housing (1444, 1844, 1944) and the opposing engagement surface is a surface on the drive shaft (1436, 1836, 1936). a drive shaft (1436, 1836, 1936) movably coupled within a bearing housing (1444, 1844, 1944), wherein the drive shaft (1436, 1836, 1936) has a first end and a second end; a rotor coupled with the second end of the drive shaft (1436, 1836, 1936); a stator coupled with the rotor; and a bearing assembly interfacing engagement between the drive shaft (1436, 1836, 1936) and the bearing housing (1444, 1844, 1944), the bearing assembly comprising: a plurality of spaced-apart polycrystalline diamond elements (1501, 1801, 1901), wherein each polycrystalline diamond elements (1501, 1801, 1901) has an engagement surface (1513, 1813); and an opposing engagement surface (1515, 1556, 1815) comprising a metal, the metal comprising at least 2 wt.% of a diamond catalyst or diamond solvent based on a total weight of the metal, wherein the opposing engagement surface (1515, 1556, 1815) is movably engaged with each of the engagement surfaces (1513, 1813); a plurality of spaced-apart polycrystalline diamond elements (1501, 1801, 1901), wherein each polycrystalline diamond elements (1501, 1801, 1901) has an engagement surface (1513, 1813); and an opposing engagement surface (1515, 1556, 1815) comprising a metal, the metal comprising at least 2 wt.% of a diamond catalyst or diamond solvent based on a total weight of the metal, wherein the opposing engagement surface (1515, 1556, 1815) is movably engaged with each of the engagement surfaces (1513, 1813); wherein the plurality of polycrystalline diamond elements (1501, 1801) are coupled with the drive shaft (1436, 1836) and the opposing engagement surface is a surface on the bearing housing (1444, 1844), or wherein the plurality of polycrystalline diamond elements (1501, 1801, 1901) are coupled with the bearing housing (1444, 1844, 1944) and the opposing engagement surface is a surface on the drive shaft (1436, 1836, 1936).