Well, 80% of the sway. I'd already removed the tires and added axle shims to my 5400 series loco but that didn't help the back end of the loco going side to side down the track. As it turns out the second and fourth driver axle VERTICAL play is quite sloppy on this model. Combine that with sloppy siderods and you get a very wobbly loco. Guess Rivarossi ran out of axle bearings.
My solution was simple. There is a channel cut into the plastic axle cover corresponding to drivers 2 and 4. I filled these out double layers of vinyl electrical tape, reducing the axle vertical movement by half.
Also weighting the loco by a few ounces helped too. Before I did this, with the tires gone the drivers spun with the slightest pressure of my hand. Now she fights me. I've made a real loco out of this one.
Robby
PS--I replaced the bulb with a yellow led wired with a 470 ohm resistor. Now I have a constant brightness headlamp that comes on full at 2 volts.