k-line GG1 frustrated

Do you have the springs and washers assembled correctly?

I have one that I converted to TMCC/RS.  The hook that limits travel should have a large washer in each side of the spring.  I also have a nylon washer about 1/16" thick on top of the truck mount under the mounting screw head.  You might have to form the hook a bit, depending on exactly what issue you're having.

Mine has no problems, even on pretty lumpy track runs.

Yah I got the springs in the right place and the large plastic washer which is why I'm so baffled by this re-assembly problem. I've also noted that the couplers won't stay locked 

The only variable would appear to be the angle of the hook, that will determine how much play the leading and trailing trucks hve.  I'm assuming the frame didn't get bent, that would be a whole other kettle of fish!

I have this exact GG1, and it's a great little locomotive, but it has also had some issues.  The Battery harness was wired backwards so that when the power to the track went off, there was no sound, instead it was just killing batteries.  Once I swapped the wires in the connector, it was all good.  It runs on my O36 just fine but the wheels of the truck do climb out on O27.  I did have the screw that holds the coupler in place fall out, and after a search we did find all the washers and springs that held it in place and got it back together.  I can take photos to send you/post here if you want in order to make sure you got things in the correct fashion.

My K-lines tab always popped out of the slot too. It took a couple unexpected dives warranting removal, and straitening of the front truck wheel frames. While there, I took time to lengthen the groves to make o-27 turns, tweak the pilot step tabs, and coupler tabs too. (Grab/bend tabs only). Removing the trucks, and tweaking tabs while resting on a test track was worth the effort. Ended with better tracking than ever.(I must also use a caboose, equipped with long, articulated couplers, placed between the GG1 and other cars just to be able to pull a train around 0-27 curves) Helped a lot, but I still try to avoid allowing the pivot between the trucks to sag when handling. If you don't use grades and have very flat track, consider limiting the pivots ability to "sag" or rise with washers, or a screw modification.

The climb out may be the slots limiting the pilot swing and/ OR the 3O"+dia.coupler design extends too far beyond the curve centerline for leading "standard" coupler cars to be pulled correctly. Binding causes lead cars to climb out too. That is why I run the custom "head end" caboose on GG1 freight for 0-27.

ok go ahead something is amiss 

I just worked on one of these. I noticed the couplers have a small second screw that locks them in place to the pilot truck. I found the screw had been removed from the opposite truck and the coupler swung freely. That might be a simpler mod and allow even more movement than milling out the slot.

Pete