Any suggestions on a solution for this?
There is about an 1/8" drop, mounting screw is tight. Sag is so great it requires tape on the "thumbtack" bottom to prevent shorting out.
Thanks.
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Got the same thing on an MTH bobber caboose. Just haven't had time to dig into what the deal is. I'll look tonight if I don't work late.
The Atlas couplers have 2 screws that share the same threaded hole. To fix your droopy coupler:
1. Remove the truck from the car.
2. On the bottom of the truck, loosen the screw that hold the uncoupling armature. This is the screw that goes through the coil spring.
3. On the top of the truck, tighten the screw that holds the coupler to the truck. The screws in steps 2 and 3 share the same hole so if the bottom screw is too tight, you won't be able to tighten the coupler mounting screw on the top.
4. After the top screw is where you want it, tighten the bottom screw.
This method has worked for my Atlas cars that occasionally develop a loose coupler.
Thank you Bob, will go at it this evening.
After reading this thread I checked one of my Atlas O NE-6 cabooses. First picture shows pitting on one of the thumbtacks that evidently had been making intermittent contact with the middle rail. The clearance between the thumbtack and rail was very small and slight downward pressure on the coupler caused it to contact the middle rail. I slightly loosened the coupler drawbar (larger phillips) pivot screw, removed the truck (smaller phillips) pivot screw, and gently pulled the truck out from beneath the car. I then turned the car upright and tightened the slotted upper drawbar screw. I retightened the coupler drawbar pivot screw and reinstalled the truck pivot screw. The thumbtack now has about 3/32-inch clearance from the rail and does not deflect when slight downward pressure is applied – same as at the other end of the car.
Note: the coupler drawbar pivot screw has a spring underneath, so release it carefully, although the screw does not have to be removed to do the repair.
MELGAR
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@Bob posted:The Atlas couplers have 2 screws that share the same threaded hole. To fix your droopy coupler:
1. Remove the truck from the car.
2. On the bottom of the truck, loosen the screw that hold the uncoupling armature. This is the screw that goes through the coil spring.
3. On the top of the truck, tighten the screw that holds the coupler to the truck. The screws in steps 2 and 3 share the same hole so if the bottom screw is too tight, you won't be able to tighten the coupler mounting screw on the top.
4. After the top screw is where you want it, tighten the bottom screw.
This method has worked for my Atlas cars that occasionally develop a loose coupler.
That was it Bob, thank you! We have removed the skid plate tape, "Old Sparky" is no more!
@MELGAR posted:"After reading this thread I checked one of my Atlas O NE-6 cabooses. First picture shows pitting on one of the thumbtacks that evidently had been making intermittent contact with the middle rail. The clearance between the thumbtack and rail was very small and slight downward pressure on the coupler caused it to contact the middle rail."
MELGAR
Until we saw the sparking when running in the dark, we had no idea the cause. Nice caboose.
Glad that it worked for you! 
Will this also work on Lionel? I've got a Lionel caboose where the couplers are so low that the knuckle falls out under the joining coupler over less then perfect track.
@sinclair posted:Will this also work on Lionel? I've got a Lionel caboose where the couplers are so low that the knuckle falls out under the joining coupler over less then perfect track.
Lionel has used several different coupler mounting methods over the years. If you remove one truck from the caboose, take photos of the top, side and bottom of the truck/coupler and post the photos here then we can try to help.
