Open it up and take a look

The easiest thing would be to open it up and take a look.

First remove the plastic clip the on the top just above the left hand wheel in the photo. Then flip the gearbox over and remove the long plastic clip on the bottom. The easiest way to remove the clips is with very small flat screw driver. Slide it under the side of the clip and twist the screw driver slightly to bend the side out over the protruding lug.

The gear box should then split in half down the middle. Examen the gears, there probably is a broken piece of plastic or other debris jammed in between the gears. You should take the gears out and clean them good so that you can examine carefully for cracks, broken or deformed parts. Cracked gears on the drive shafts were a common problem with P2K locos. I had to replace six axles on a total of four locomotives (I used Walthers parts). These are very common gear boxes so if there is any of the other gears damaged there are several sources (Athearn & Walthers are a couple of them) of gears.

Clean the good gears well and replace damaged ones. Reassemble the gear box and very lightly lubricate with a plastic compatible grease. It should move freely now.

Cracked axle gears

When the axle gears first start to crack they make a clicking noise, but when are fully split they will spread open enough for the teeth to jam as you describe.  Solution is to replace all of them with new gears from Athearn (#60024) or Walthers.

Scott Chatfield

Thanks

Thanks, RMeyer and Scott- I had done a full disassembly, inspection & lube before posting. I did find that the axle gears have a split, but I assumed that they were made that way. Apparently not... Thanks for the info, and the part number.

Before I proceed...

Before I proceed with replacing the axle gears, I thought I should post again with a clearer picture. If you look at the image you can see the split in the gear. I think maybe this is the way they are made, so that they have some springiness to grip the axle. All axles are the same, & it seems a real coincidence if they all went at the same time. I asked my local, George's Trains in Markham, to set some aside, but now I'm not sure.

What do you think?

(PS - aren't macro lenses handy?

Split = bad

No, they are definitely not designed that way.  The problem is the plastic can slowly shrink over time, while the steel axle does not.  Guess which one wins that fight?

Pretty much every old Proto:1000 and Proto:2000 loco with the Athearn clone 4-axle drive has 100% failure of its axles after 10 or so years.  A lot of Athearns from the '90s had the same problem, 4 and 6 axles alike.  And even though they use a different drive with skinnier axles, even a fair number of Atlas and Katos had that problem.  I've replaced gears in all of them, but not 100% of them.

Scott Chatfield

Replace

Classic split gear problem.  When they split, it often isn't even noticeable except under magnification.  The photo showing an obvious crack running across the entire axle suggests the problem is severe enough it could jam the whole truck.  I've had more than one example of a Proto 2000 mechanism where every axle gear needed replacement (and as Scott noted above they are definitely not manufactured that way, so any split component must be replaced).

Proto split gears

Hi Dave,

Plenty of advice within this forum, on the 'net and also YouTube videos. Replacing the gears is an easy job with Athearns and you should be able to get replacement gears from your local hobby shop. Athearn pt no is #60024 in a packet of six, so two packets will do three B-B locos. I just went through the exercise over the last couple of months and replaced them in 16 of my P1k and P2k Geeps and F-units. Also refer to Phil Hartung's excellent article p71 of the latest issue of MRH (March-2021).

BTW: I said above "an easy job". First one was the hardest!

Thanks, all

Lots of good direction here - thanks.

I found the article on this in the March 2021 issue the same day as my last post. figures... ;^)>

Followup

I did get some gears and replaced the split ones. i hit one small snag - the gears are so tight that when I finally got them to go, they went suddenly & two would up jammed against the bronze bushing ("bearing") and jamming the wheels in a totally new way. Easy to fix.

So - I tested it out in DC (I had un-soldered the 4 power connections to the decoder & removed it) and then re-soldered the decoder. Even did the tidiest install I'd ever done. Unfortunately, I failed to notice that the handling had knocked off one of the speaker wires, and it contacted the frame and blew up the decoder as soon as I put on the power............

Tad frustrating. But - live & learn.

. . .

What is that saying ?  "  When in rains  it ...  "

Marc

Or as I say - It's either a

Or as I say - It's either a drought or a famine...

Big believer in Murphy, me.

Turn the wheel while pressing it on the axle

When I press a wheel on the axle, I normally turn the wheel while pressing it on, much like if I was trying to screw the wheel into the axle.  I find I get much better control than just straight pressing alone  It also helps when using newer replacement gears as it can be a challenge to get the wheel started into the axle.  If you press the wheel on too tight or the finished axle is out of gauge, turning while pressing or pulling makes it much easier to get finer adjustment.

Since axle cracks can often be hard to see, one thing I do as a quick test is grab each wheel and twist in opposite directions.  If you can twist the wheels without much effort, the axle is most likely cracked.  It should take a fairly strong grip and twist to move the wheels if the axle is good.

Craig

Jammed gears

I had the same problem on early Athearn and also on early  Proto 2000 gears. Investigation revealed that the gears pressed onto the axle was the problem - very tight fit and splitting.  I purchased new gears and found that the new ones were also a very tight fit onto the axle and after fitting one new gear it wasn't long before that gear split. To overcome the problem I purchased a drill bit that just fitted into the gear. Placing the drill bit into my drill I then more or less reamed out the gear hole and refitted the axle shaft. The fitting was not that tight but held firm, and after re- gauging,  I just added a small amount of Loctite to the edge of the gear. After that I had no problems. even to this date. I did this some 15-20 years ago and still do, and have not had any problems with the modified solution. Even today on some  new locos [Australian models] some of my friends had the same problems however as they are under warranty just returned the loco to the dealers for fixing..

By Reaming the gears

You have removed the base tensile stress in the plastic gear.  That is a side effect of the design that requires an interference fit like these and many other applications in model rail applications.  This stress leads to the failure due to a cyclic condition.  P2K decided to increase this interference fit, the metal axles are slightly larger in diameter.  Thus increased the stress level. The higher this stress is the quicker the cyclic failure.  Athearn units with this same type gear fail as well, just not as fast because the interference stress are lower.
By eliminating the interference, you have reduced this base stress to zero.  The loctite conducts the torque stress from the plastic gear to the metal shaft much like the interference fit did, but without the base stress level.  They easily could have infinite life.  This is a great solution to a nagging problem

You would think that all these years of experience ...

The manufacturers would know what a proper fit is. Maybe they like selling parts. 

Maybe they like selling parts. ?

   They don't stock parts so probably not. They might be making products fail because they've discovered we'll still buy more  :> ) ....DaveB

Maybe there is Hope

I have an old HOn3 PSC shay that has a spilt gear. Maybe this solution would work?

Add this to the someday pile of things to do.

Thanks for experimenting,   Jack