2-8-0 Woes

[Irbricksceo]

My 2 2-8-0's have never been the most stellar performers. Both have ridiculous starting points (40/128 and 48/128) compared to my other locomotives, none of which exceed 20 with the SY 2-8-2 smoothing out at 3. They are incapable of crawling  and have always had a slight lateral sway as they moved. However, one of them has developed a problem that renders it unusable.

The locomotive suddenly became jerky, thumping every half revolution, stalling on occasion, refusing to move before hitting 55/128 speed steps and even then being jerky. As it goes, it makes a thump and jerk every half revolution. I've taken the shell off and separated the part of the chassis with teh motor from the part with the wheel assembly and see nothing caught in the drive however taking just the part with the wheels and free turning them or having that part pushed around by another locomotive showed a sticking point about every half revolution so the issue must be there. Any ideas?

[electrical whiz kid]

Sounds like a transmission problem to me.  You maybe have a loose system or it could be a bit of crud that got into the gearing and is raising hell with the performance.  In the starting issue, receiving a locomotive and taking it out of the box, starting it is probably an invitation to frustration.
It has been said here many times that you should take things apart to inspect them, lube [it] up properly with the proper oils/grease.  If you had been in the service-especially combat, this should be second nature to you.  Those M-16s needed constant care, lest they jam up in a fire fight.  You wouldn't be happy in that situation...
Check the wheel gauge, make sure those wheels are in proper gauge.  run it upside down to check the gait.  This only for steamers. 
If problem persists or is incurable, contact service dept.  Thy will help you much better than can I.
RIch C.