I find it inexcusable, today most probably not valid any more, the introduction of the 5 pole high efficiency motor as most locos are replaced with a newer type C- Sine motor and all drive axles on diesel and electrics.
the new design 5 pole motor and particular its brush plate hadn't been modified, it would have been easy to add a ball bearing (Märklin attempted to improve the squealing over the years by using metals which had a chemical reaction (motor side),
as it will eventually go out of production Märklin hasn't bothered doing anything about it, the brush plate brush holder is still inadequate in its design and no engineer at Märklin has bothered to look at it or correct it to make sure the design of the brush holder is accurate in relation to the armature (90° angle), they've improved it slightly by reducing the pressure when the brush holder is pressed onto the brush plate (this in turn used to lift up the brush holder at the end and therefore changed the angle of the brushes in relation to the armature by at least 5° ( you may noticed it in the past when you exchanged a brush it was worn on 1 side more than the other side.

John

Are you referring to the 6090 motor introduced in the last century (before the C-Sine motors)? Or to the new can motors introduced this century to replace the C-Sine motors.

The 6090 motor made Marklin a unique brand as Roco, etc. had already been using can or open frame motors. Even considering the squealing when oil begins to dry out, they have better torque than the can type because of the armature gear. I've never installed ball bearings and I have just a few locos with chronic squealing, so I just put a drop of oil on the brush plate and the motor side and it quiets them down. If my track route was much longer like John's, it might be aggravating.
I think some of the reasons the can motor has displaced it is design packaging. With speakers and larger pcb boards, it saves space, especially with smaller models. Or,do cardan shafts require extra space too?
The first generation C sinus motor was expensive to produce,so I doubt we'll see it again. Does Lemaco even use one?
When I realized the 6090 was history, I ordered enough spare brushes to last a long time. With a large enough collection, I don't run them all often. Probably not often enough. A long time in the display case and they may require some attention to get them running optimal.

I feel the same way about many of the new can motors. I have had a few fail and they are inexpensive and easy to replace, but they seem wrong in such beautiful, highly detailed and expensive locos.

Yes I do. My 37015 was one of my earlier models with a cheap can motor and it was my first one to fail.

I was not yet aware of the problem where grease from the gearbox could migrate into the motor and cause it to fail. In that model the motor and gearbox are quite close together, and I think that makes it more likely to happen.

I learned about that concern here on the forum and I am now much more careful not to over grease the worm gear. Some of my locos come from Marklin with no visible grease in the gearbox and some have way, way too much. I now always check that before running them just to be safe.

I agree. We need to use some common sense in lubricating our models and evaluate the need for lubrication case by case. I have learned that it is usually better to err on the side of too little grease, much as I do when caring for a mechanical clock.

Marklin could also do a better job of defining exactly when and how grease and oil needs to be applied. The one size fits all solution is probably never quite right for any particular situation.

Märklin should start to use a grease that is better suited for modern locomotives. note that in some locomotives Marklin has used a different grease, but they don't have any information about it.

The Trix "special" grease is just a standard cheap industrial grease intended for diggers, bulldozers, ship deck machinery etc. It's not a bad grease but there are more suitable greases. e.g that has higher dielectric properties, longer lubrication intervals and contains fewer non-relevant additives etc. e.g model locomotives don't need grease that can withstand extreme pressure or high resistance to water washout........
Ref the Safety data sheet for the Trix "special" grease 66626.

There might be some challenges to ensuring backward compatibility with the current Matrix grease and oils etc, but as long as you are aware it should not be that hard.

You can see that the former Trix desings use a white Lithium type of grease, and these had cardan shaft drive design from the originals.

One solution to the excessive 'Squealing' in the DCM is to change the end shield plate. They only need micros of wear to the plastic bore to produce the noise. New ones are available on Ebay de etc. It is a different story if wear in in the chassis block. However the chassis is more robust than the end shield as diecast apposed to plastic.

I could never see the reasoning to the roller bearings in the end shields. The roughness is actually in the gear train, especially with a little wear. All those gears with maybe slight variances to blue print, causes gear miss match, roughness and noise. It was obviously one reason Marklin did away with the side gears, made mechs far quieter for the sound age.