I have seen many posts throughout the years about cracked and broken locomotive gears. I never really read them with interest because I didn’t feel it affected me. Now that I am getting more time to run trains I am beginning to have some occasional problems such as derailments, electrical problems and so on. My two part question is what are the symptoms of a cracked or broken gear and what locomotive brands are prone to this?
- You’ll hear a “thump, thump, thump, thump” at regular intervals related to speed
- A few early (Pre-Walthers) Proto 2000 locomotives - e.g. GP7
Tom
The main culprit has always been the blue box Proto locomotives, namely the Geeps (GP7, GP9, etc.) and the SD series (SD7 and SD9). The tell tale sign is a thumping as the locomotive rolls down the track.
I have read where others see crack gears on other brands and types, but the Proto Geeps and SDs are the main culprits.
Usually though this does not result in derailments or electrical problems, so you may have other issues as well.
Rich
I have seen the rare blue box Athearn do this as well. Not as common as the early Proto engines though. Some of the Bachmann engines are prone to it as well, especially the 3 truck Shay logging engine and the 2 and 3 truck Climax. NWSL makes/made a metal replacment gear to fix the Shay issues. In On30, the Climax and Shay are also prone to geartrain/drive line issues. Athearn also had issues with the USRA Pacific and Mikado having split axle gears and the coupler between the flywheel and motor splitting. NWSL has replacement gears for them. In the brass world, many early models made by Samhongsa and Kumata have issues with gears splitting and NWSL has replacements for those as well. Mike
There was also a run of blue box Athearns that had the gear problem SD45, SDP40, and the SD40-2, I think it was the late 80’s?
I have 2 of them, an SD45 and an SDP40. The usual thumping sound, and a slight bouncing or jumping of the truck with the cracked gear.
No derail or electrical problems.
Mike.
The split occurs in the hub of the gear where it fits snugly against the axle.
The rythmic thumping can occur if the split extends into the ring of teeth but that doesn’t always happen. The thump results from the slightly wider gap in the one pair of teeth as the driver gearset jumps in the mesh. Until the split reaches into the teeth of the split gear the locomotive will appear to run fine. There is no differential gear action in these trucks, the two axles lock together through the worm gear.
The split does cause the axle gear to slip leaving no drive to that axle. When both axles on the truck (diesel) split you get no drive from that truck.
In the case of the Spectrum Shay you get no symptoms until the traction from trucks with functioning gears is insufficient. There is no differential gear action there either, the drivers are all linked to the one worm gear.
Usually, the split causes the gear to lose grip on the axle. Turning the locomotive upside down you will be able to move the driven wheels that have the split axle with just your finger. Certainly for the Shay you can do this.
You can also test with one of those brass wire power units applied to the drive wheels when upside down (or just wires if you don’t want to clean the wheels). The wire brush should develop enough resistance to stall the slipping axle.
Just a note on the NWSL gear kit for the Shay: their instructions are not easy (probably impossible) to follow with any chance of success. The interference fit of the metal gears is far too tight to get the new gears on using needle nosed pliers. By now the plastic bits used to clip the drive shafts to the trucks are so old they have little to no flexibility and are secured by tiny plastic moulded in projecting pins less than 3/64" in diameter that actually hold on the driveshafts. These old plastic bits are in the way and cannot withstand much force. Not a design to emulate in future. The truck frames are metal.</
This has been my experience with cracked gears.
On the Proto-2000 GPs it is an easy fix.
-Kevin
It’s more like a “click, click, click”.
That’s by far a more common symptom than the rythmic thump.
If it’s a Proto 2000 GP get a set of replacement axles from Walthers. 10 minute drop in job if you’re careful. The snap on plastic axle retaining plate on the bottom of each truck needs to be very carefully pried off. It’s held on by wedge clips moulded into the gearcase (truck body) that click into rectangular holes in the mounting tabs on the retaining plate. Have a careful look where these four tabs are snapped down before you try to pry them off.
Have s gp 18 doing that . What athearn gears could i use since i have spare parts? Proto gp18
I really appreciate the great answers I got, I know what to look for and am fixing my other problems. I figured out my derailment problems…turnouts because I haven’t installed manual throw switches or electrical ones I am going to use for my mainlines.
Athearn #ATH 60024 is the part number. The gears are widely available.
Rich
This is one of those topics that should be stickied somewhere since it comes up every few months.
If you want you can also buy new wheelsets with the proper gears attached. These new wheelsets are a bit better quality than the old 1980’s-1990’s ones. Walthers also sells larger wheels for the old LL Proto E-units.
BTW in my LL GP-9 I didn’t get a thump or click but more of a grinding sound that came and went. I suspect at times the wheels quit turning and the gears were grinding or something.
I have experienced this on a BLI N&W A class. I gather at some point around 15 years ago they used a type of plastic that contracted as it cured long term. It does manifest itself as a click click synchronized with the wheel rotation.