The feet replacement parts are available from the distributor.
https://www.boschmixers.com/product-category/parts/bosch-universal-classic-parts/classic-mixer-parts/
Some of the very few parts available new.
Dave
Those are for the 86-2009 version, mine is the 1972-1986 UM3 design. I haven't found anything on it that is certainly a date code, but if the number stamped on the side of the motor field coil assembly is a date code it was made in the 42nd week of 1972.
All of the soft rubber parts on my UM3 are degrading, and there are no new soft rubber parts available, but i ran the feet through an ultrasonic bath and scrubbed them with a brush, and they are tacky again.
I did some exploratory surgery last night. The transmission looks fine from the outside. Some of the parts diagrams refer to it as "oil filled" and it has an oil seal which is a standard industrial part, but most of the rest of it is no longer available. I would need a sturdy set of split ring pliers to go deeper, but i'm not sure i want to. I over-tensioned the belt when i reassembled, so I'll need to fix that before i use it again. No big deal now that i know my way in and out of the thing.
A set of pulley pullers of the right sizes are required to disassemble the motor, as it's captive by the high-speed drive on the top and the drive pulley at the bottom.
I may try to replace the motor base with one from the early 2000's if this one starts sounding bad again, but as i've said before it actually sounds better now than it did when i bought it from a thrift store probably 25 years ago. My best guess is that it had sat for a long time, and i eventually warmed it up enough to melt caked grease? who knows. I assume there is a ball bearing at the bottom of the motor where it drives the belt. The top has a simple bushing, so i applied some bushing oil and ran it upside down for a bit.
I still have no idea what the failure mode is on old UM3s that sound like a rock tumbler. Maybe the bearing at the bottom of the motor?
UM3 parts are sold here as well:
https://www.mykitchencenter.com/shop/Small-Appliances/Small-Appliance-Replacement-Parts/Stand-Mixer-Replacement-Parts/Bosch-Replacement-Parts/Bosch-Universal-UM3-Replacement-Parts.htmThis guy's video is informative but it turns out that you don't have to take the knob off at all.