I would take the last SD80MAC over to your workbench, remove the couplers/shell and try to see what's causing the issue.
If you have a strip of track with a power source nearby, that would be great for troubleshooting.
I recently had a problem with an atlas Alco rs1. Turned out the motor was ever so slightly loose. It rocked against the frame and made an awful noise. I doubt it's that based on the pitch of the noise. I would second the notion of a binding or a rubbing of the flywheel. Perhaps plastic on plastic or metal to metal rubbing? I think you might have to rip the thing apart and look for little "things".
JJF
Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing.
Yesterday is History.
Tomorrow is a Mystery.
But today is a Gift, that is why it is called the Present.
My first thought, something might be binding. Possible in the gear tower or perhaps the flywheels either rubbing the frame or motor housing. possible flashing problem On a gear. my other thought is one of the bearing points for the gears is a tad to small or has flash in it binding the axle the gear is on.
shane
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
Hi all! I purchased 3 SD80Mac from Athearn Genesis. All of the same run. One runs buttery smooth, super quick. Another is smooth but slower. The last makes this awedul screeeeeetch around the entire track and is slower than the other two. Its a constant high pitched sqweal.I have oiled all bearings, got special stuff for the motor bearings and commutator. I have applied grease through the worm gear but never taken apart the trucks. Both directions I have this problem. Can someone point me where to go?