Beginning in roughly 2019, Whirlpool (operating as KitchenAid) has significantly reduced the amount of grease put in to the mixer’s gear train when assembling K45-type models (the “Classic”, “Artisan”, and other models similarly constructed).
The factory service manual specifies six fluid ounces (a nominal 3/4 cup) of grease of an appropriate type, and has done so since this model type was introduced decades ago. The quantity of grease serves several purposes: in addition to creating a lubricating film on the gears and other moving parts, the additional grease serves as a reserve to help in the uptake of wear products, and helps the gears run nominally cooler. And finally (but notably), the grease also changes the acoustic signature of the mixer, causing mixers with the appropriate grease load to sound little bit quieter.
Here are a couple of photos from a 1970s-era Hobart K45. In this instance, the grease has significantly thickened and hardened with age, but it’s clear that the gear case was significantly filled up.
This grease load is typical of mixers manufactured up to the late 2010s. (In fact, there was more grease in the gear case than is shown here; some of it came out in chunks when the case halves were separated.)
In contrast, here’s a mixer of the same type, manufactured in 2023.
The absence of grease left in the upper housing is clear, as is the significantly smaller quantity of grease on the gears.
While there’s no specification or measurement for the amount of grease that KitchenAid is currently using in new or refurbished mixers, it is clearly a great deal less than in years past.
This shortage of grease is relevant, because the reduced lubrication accelerates wear on the “sacrificial” worm follower gear, and hastens its early failure. This has resulted in mixers coming in for repair prematurely, often within the first two or three years of ownership.
My recommendation is that if you have a mixer of this type, and it was manufactured (or purchased refurbuished) starting in 2019 or later, consider cleaning and regreasing the gears. This will improve the longevity of the internal parts in the gear case, and give you a chance to inspect the mechanical parts for premature wear or signs of failure. During reassembly, refill the gear case with the proper quantity of appropriate grease (6 fl-oz, NLGI #2, NSF H1/ISO 21469 rated).
Here’s a list of parts and materials for the job.
Related cost reductions: Pinion drive bearing and rear bearing bracket.