If the shay gets off track in  or after curves the outer shafts may be worn and tend to bind.

You can use the 13 teeth steel Shay gears from NWSL for replacement for the Climax 12 teeth. Just have to glue them on as the hole in the gears in bigger than the hole in the original.
I had 5 of 6 gears that were split and replaced them with the shay ones. The locomotive runs very well now. Mine didn't run at all out of the box but sending it back was out of question as I bought it few days ago and the engine is not produced anymore or not for now.

My trucks on the engines are able to rock backwards and forwards.
And I found some reasons for derailment. The first is the most important, that the outer shaft is made of plastic and the inner one is metal. If there is binding that's because the inner shaft is stuck in the other one (45° turned inside) and this doesn't allow the shafts to slide anymore and it's hard to pull the shaft out without destroying the plastic. A metal outer shaft would be the right thing for this engine. The forces in the driveline are too high for inadequate plastic.
BUT WHY JUST ME!!!!!
The other thing is that some of the trucks run like crap they don't roll downhill they egg roll downhill.
I disassembled the bad ones and reassembled them correctly now the run well.

Yes returning it would be OK and easy but I bought all in Germany and they got their locos from I don't know it would be much easier if I bought them at my local dealers but he was told they are out of stock from his dealer.
What if suddenly all these shays begin to derail? What a chaos if everybody returns his loco(s), so I will keep investigating.
What about that pivoting tendertruck? Intended to pivot or not.
By the way, are there different boxes these shays are delivered in? The most I saw were some big ones with foam in it.

Everything is in working condition and can move or pivot freely. I  tried with oiling changing trucks and..... but no result. The gears are in perfect condition no cracks, no bent axles, good moving shafts. I also read here that the tendertruck is not intended to pivot but my truck pivot all of all unit. Does anyone have an e-mail from Bridgette cause a call from here would be very expensive.(Luxemburg Europe)

Everything sits where it should, lubed what has to be lubed, the trucks can pivot freely.
By going into reverse when the truck starts to lift it goes back to track and the journey can go on. But thats not how it should be. From 5 units only 2 do the job how it should be. It's a bit sad that I had to buy 5 for having only 2 working locos. I've checked everything but with no result. It seems that the binding comes from the shaft that comes from the engine to the truck cause while running slowly and lifting truck, I can feel that sometihng is binding and the truck doesn't move freely anymore until reversing to release the force in the shaft. So any ideas?

Hello,
I wanted to know if it is a known problem with the 3-truck shay that the middle truck gets off, lifts from the rail in curves and even on straights. There seems to be a torque transmission problem that the truck is pushed out of the rails. Only by holding the loco down with hand applying some force keeps the truck down. Is there a solution to fix this?
Thanks

Hello,
I own 5 of these shays and on everyone the tendertruck can pivot. The screws are well tight but the truck can pivot. How is that possible.
Now beeing at the trucks I have some weird things that happened with these shays. One after the other began to lift the middle truck in curves and some even on the straight line. Even when glueing the tendertruck to the frame. I remarked that the torque applied on the shaft doesn't give the truck the chance to stay on track the force pushes the truck out of the rails even at very low speed. Is that a common problem?
The funny thing is, that my converted 3 to 4 truck shay is the best runner and here from the beginning on I fixed the 3rd truck because of torque binding problem lifting the truck.