What does this sound mean

It means for the love of trains- oil the motor and gear bushings!!!! The squealing sound is the motor spinning at speed instead of smoothly turning floating on lube, it grabs and is rapidly destroying the bushing. Again the motor being geared, spins fastest, the gears next fastest, and the wheels and axles the slowest.

Specifically both sides of the armature and each of the gears right on the pin or shaft they ride on.

Also, you want the axles but hit those points above first. I use a needle oiler with medium weight oil. Do not get oil on the brushes or put more than a drop on the brush side of the motor.

Here is a 2026 video I found, starting at the 5:30 minute mark begins the lube with a needle type oil bottle https://youtu.be/wVGNjpJRaTQ?s...A7FUhZeBB0&t=329

Again, 2 very important things. You want to get oil into those bushings- yours are bone dry from the horrific squeal, but also the higher voltage it took to even get the engine to move. You were literally turning electrical energy into friction in the bearings and heat. But at the same time do not over oil. You only want the oil directly on the bushings and pivot points, not dripping and flinging everywhere as the motor and gears spin at high speed. That's why using a needle oiler is the best way, giving you that ultimate control to put just the smallest drop of oil where needed- but not get and drip oil into everything else.

And last, above all else, you don't want oil in the brushes. I've seen someone who did not know oil them.

This side picture also better shows the hidden gear that the motor gear is driving for more gear reduction.  Again, that shaft or pin that the gear rides on is barely visible between the 2 wheels- but that could be partially where the squeal sound was coming from since that gear spins faster on that shaft than the much more visible gear above the wheels.

Pictures from this 2026 restoration topic https://ogrforum.com/topic/85339364473714657

Wow, great advice and guidance Vernon. Dumb question, what is a bushing?

Ignore my bushing question. I looked it up. Sorry for not doing so first.

Vernon, as you knew, your advice was spot on. See (and listen to) video below. Now, if you don’t mind helping with my continuing education into this amazing hobby…when the e-unit is active, it is noisy. When not engaged, it runs much quieter. (See second video below). Is that just the way it is or is there something I can do?

Thanks for your patience, Bill

I messed up attaching files. The third one is quieter.

E-units (these older electromechanical ones) tend to be noisy. That's normal and not a ton you can do without going down a path of modifications. It does have the off switch- that's what I normally do.

https://ogrforum.com/topic/buzzing-e-unit

https://ogrforum.com/...-rid-of-e-unit-noise

Thanks again. Keep well.

Don't forget the axle bushings.  If you turn the loco over, you'll see "cut-outs" on the bottom that show where the three main driving axles pass through the frame.  The frame itself is made of sheet steel, but there will be thick steel or bronze surfaces where the axles pass through.  Put one drop of oil on the axle at each bearing and move the wheels back and forth to "work it in."

Although the axles turn slowly, if the bearings are allowed to wear egg-shaped from a lack of oil, the gears won't engage correctly, and it will lead to a full rebuild down the road.

The most popular mod to quiet the E-Unit is to run it's coil on DC.  It has been said that this can cause the core to get magnetized and eventually start sticking, but it's easy to bypass the diode and demagnetize it.