This is one of my work horses that has operated for more than 8 years... say. When last week while pulling a load of 8 cars, the locomotive went into spinning the rear wheels (trucks) and the front wheels (trucks) not spinning. Got it back into the maintenance shop and found that the front drive shaft separated from the worm gear shaft. See image. (https://i.pinimg.com/736x/22/9d/32/229d3268010e5416ab944459aa2bbfaa.jpg) Thought this would be a simple fix, that is, just slip the connecting rod (yellow lined) back onto the worm gear shaft and all would be well. NOT! I put the locomotive back on the track and within say 10 track feet, it slips off again. I tried glue on the back side of the shaft (motor side), but that failed. So I'm at a lost as to how and/or what keeps the shaft connecting rod in place. I don't see any issues with the other shaft and I also don't know or see what's keeping the other connecting rod on the worm gear rear trucks.
(https://i.pinimg.com/736x/0c/76/1f/0c761f661ffab7a824edc71c750630fa.jpg)
I'm missing something, but I'm at a lost at this juncture. Oh, Bachmann doesn't have that connecting rod (yellow lined) piece as an individual piece to purchase. So, can anyone inform me of what I'm missing or advice on fixing this issue?
Perhaps you did but check Ebay Ralph, lots of parts (and assemblies) listed for diesel repairs.
Also, while the drive shaft is off, rotate the worm by hand to make sure nothing is binding up the gears in the truck at some point in their rotation. If the gears bind, keeping the worm from rotating, the drive shaft will pop off.
Len
It looks like there may be too much play in that truck.. One nice thing about Bachmann diesels is that the trucks can be tightened just like a freight car. The bolster screw sits on top of that round piece above the drive shaft. Put the drive shaft back in place, then tighten the bolster screw to reduce the play in the truck. Don't over tighten as too stiff a truck will cause derailments just like with a freight car. If you encounter this problem, back the screw off in quarter turn increments until the derailments go away.
If this doesn't solve the problem and the drivee shaft still keeps slipping out get a slightly longer one. They are available from Bachmann parts you just have to look under the listing for each individual locomotive type to find them, because they often have a different part number than what is on the diagram that came with your locomotive. The listing in parts will tell you the length of the shaft, like 20mm for a GP30 or 30mm for a GP40. They are pretty cheap, $1.35 each, so you might want to go through all the locomotive pages and order one of each length you find. That way you can test fit them in any locomotive you have this problem with.
Gentlemen, you're hired! The trucks and worn gear, found no binding, i.e., they were free rotating. With J Wards information, I meticulously took apart the circuit board in order to get to the boster screw (didn't know that's the name of that screw). Performed the tightening on that one front truck, then restored all parts. Performed a test run and funny thing, the rear truck axle separated. Again took apart the circuit board and found the boster screw of the rear truck and performed tightening (approx, 3/4 turn of that screw). Restored all chassis parts, and performed a test run. IT WORKED! After operating the locomotive on my main line, in both forward, reverse, a few jerking operations and 8 car loads around the layout, the locomotive performed superbly.
I am truly grateful. Of all the maintenance I've performed on my few locomotives, this is a totally new information that I would have never performed without your insight. Thank you, thank you, and thank you again.