How to fix Proto 2000 axles -- the dreaded P2K split axle epidemic.

I have quite a few P2K (Proto 2000) four-axle engines on my layout. One of them started running erratically and acted like it was going over a stray piece of ballast every inch or so. When I looked into it, I found out that the P2K engines had axles that split, leading to operating problems. Apparently, Walthers discovered this problem right after they bought the line and sent out thousands of replacements, but are no longer doing so (at least that's my understanding.)

It's a fairly easy fix to do and you don't even have to take the shell off.

First, flip the engine over and locate the long plastic piece that runs between both sets of axles. It fits over four little tabs, two on each side. You'll need to get a little flat-bladed screwdriver in there to pry up on the piece where it goes over the tab. Pry up a little bit on one, then move on to the next one. Once you get one side, you can usually just "hing" up the piece off the other two tabs.

Here's the piece right after it popped off the tabs:

Carefully remove the piece and set it aside. See the little gears on each axle? Those are the culprits.

They just lift out of the truck assembly. You may have to wiggle them a bit to get them free of the other gears, but they should come right out.

Look at the second one from the top. See the split? That's not supposed to be there. It allows the gear to flex and play too much, creating all kinds of issues.

You can buy the expensive Walthers P2K replacement parts, or you can use the Athearn SD40 gears -- they are a drop in match and are more affordable. When you buy these, just assume all your P2K four-axle engines will need replacement axles. It will save you the trouble of ordering more later.

Remove the old gears by pulling each wheel off. You may need to use a pair of pliers or grips of some sort, but if the split is big enough, it will easily slide right off.

The hardest part of this operation is getting the new gear back on. I had the best luck putting a drop of Labell oil into each end of the new gear. The first wheel can then be twisted on -- but leave it just short of where you want it. Why? Because when you go to put the other side on, it will most likely slide on even further. If you leave it short, you should end up pretty close to where you need to be. Leave the gear a bit short of the wheel itself and approximately centered.
In many cases, I had to use a set of grips that had teeth in them to grasp the gear (the teeth of the grips basically fit into the teeth of the gear) and then another pair of grips to twist the wheel assembly on. Be careful you don't damage the gear. If you mar it, be sure to file off any rough spots.
Once you have the wheels on and the axle gear centered, drop it back into place. You will need to get the square nuts on either end of the wheel lined up with each other, otherwise it won't drop down into the truck assembly correctly. This can take some practice, because when you go to put the axle back in, the little nuts will want to spin out of place.
Once it's in, take a look at how it lines up with the other gears. Sometimes flipping it over gives a slightly better match. When you have it lined up, put a drop of plastic gear lubricant on it. When all the axles are in, replace the long plastic piece by snapping it back into place.

Once it's reassembled, you are ready to go. It's not hard, but it can be frustrating until you get the hang of getting the axle gears centered on the axles. Be prepared to pull them apart a few times to get it right.

The split axle problem is apparently limited to the four-axle diesels (which I hope is true, because the six-axles are harder to get apart from what I could tell). I bought most of my diesels at the same time, and they all started going bad about the same time too.

Signs of a potential split axle may be:

• Erratic operation, such as lurching.
• Strange noises, like whining or grinding coming from the engine as it moves
• Bumping -- meaning it acts like it's running over something every inch or so.

Good luck with your repairs.