The Athearn Maintenance and Upgrade Site

What follows are simple, yet effective ways to improve the performance of any Athearn diesel locomotive model. The following procedures will require tearing apart your chooch and modifying different parts, completely voiding any warranty for the product. Proceed at your own risk, but trust me - these modifications won't hurt. They have been performed by many modelers over the years with great success. Follow the directions, keep the drawing that came with your chooch at hand and you'll end up with better power in the end.

If you're curious about some of the other brands, click on one of the following:

Proto 2000 Drives.
Kato Drives.
Atlas Drives.
Athearn Genesis Drives.
Bachmann Spectrum Drives.
I do suggest reading through the Athearn section first, as all these other drives are basically modified Athearn drives.

OK - Ready??

An Overview

The Athearn drive system. While not the most technologically advanced mechanical system out there, back in the '60s when it was developed, modelers had to deal with the likes of some real ugly drive systems of the time (alot of them in places like "top of the line" brass models). Most drives back then utilized rubber bands, plastic or rubber tubing, real primitive gearboxes or a combination of several of these, producing results varying from adequate to REAL bad. Couple all that to traction tires, basically a technique to enhance traction for very lightweight models - one wonders why some veteran modelers stuck with the hobby. Athearn, having dealt with rubber band drives, etc., developed a simple chassis design that, probably almost 40 years later, still stands as the most reliable chassis system that exists.

Virtually every diesel model locomotive out there has some variant of this system. Overland, P2K, Atlas, Kato, Bachmann and others, both HO and N scale, all share drive characteristics and similar components with the original Athearn system. Even Athearn's own Genesis SD series locos with the "all new drive system", same deal - a pair of trucks with all wheels driven and picking up power from the rails, a worm gear atop each truck connected to driveshafts with universal joints attached to each end of a motor, all built on a fairly heavy cast metal chassis to keep all wheels on the rail. Every model railroader has or has had at least one and probably still has it because of its reliability. Most of those 40 year old models are still at work on many a layout. Some of mine, albeit with new motors and wheelsets, have withstood ten years of constant use, at times for up to 6-8 hours straight. Heck, back when I was a kid, I found an FP45 buried in a sandbox at a friend's house that he said I could take, "It's busted - go ahead and take it". Real spoiled, bratty kid with more stuff than he knew what to do with, anyway. What really ticked him off was that, after a GREAT deal of cleaning and polishing by my father and I, it actually ran quite well.

The purpose of this part of the site deals with Athearn drives and what I've learned while working with them for almost 30 years. I'm possitive that experienced modelers won't find a ton of new info here, but if you're a beginner, hopefully you'll find some useful information to keep yours running well.

The Simplicity Of It All

Beginners, this is the perfect time for you to really get aquainted with your Athearn chooch. Later on, I'll offer some info on disassembling some other brands, but for now we'll deal with Athearn. Break out the exploded view drawing of your loco and a small flat screwdriver, pull the couplers loose and read on:

All Athearn locos, whether they be switchers, 4 or 6 axle locos, all share the same drive system. Some modifications have been made here and there, and they will be mentioned.


Athearn shells are mounted in one of two ways - a pair of mounting lugs on either side of the chassis thru holes on the sidesills (older models)or with four plastic clips molded to the shell, protruding thru four slots in the bottom of the fuel tank. If you have an older one, spread the sides of the shell apart gently with the screwdriver and your fingers until the shell is free. The newer models require a bit more messing. While pulling up on the shell and gently squeezing the sides, place the screwdriver into the holes and gently (and simultaneousely) work the clips until they release, freeing the shell from the chassis.

After the shell is off, compare what you see with the drawing. And now would be a good time to have some paper towels on hand. Athearn is notorious for using large ammounts of lubricant everywhere on their drives. You'll want to wipe most of it from the drive (and all of it from your hands).


Pull the metal pickup strip from the top of the motor and put it in the box (the Athearn box will do). On the top of each truck tower you'll find the worm housing covering the worm gear (where the drive shafts connect). Gently pry them off with a screwdriver - you might want to place a free hand over your work to prevent the housing from flying free. Once removed, pull the worm gear loose, followed by the drive shafts and universal joints. Don't loose the thrust washers or the bronze bearings on either end of the worm gear shaft. Do this to both trucks. Lift the chassis and the trucks should be free of the chassis. Notice which way the motor sits in the chassis. with a small piece of masking tape and a pencil, mark the front of the motor with an "f" (the direction of the headlight clip). Grasp the motor, gently pull up until it comes free from the chassis. The small neoprene motor clips will sometimes come out with the motor, sometimes not. If one or both clips still reside in the chassis, use a dull pencil to poke them out of the chassis. Be careful not to damage these clips. While their pretty tough, if they get cut or disfigured, the motor won't mount back in the chassis correctly, causing you to use my name in vain. Regardless, you should new be looking at a chassis with only a headlight bracket/light assembly attached.

At this point, if your curiousity has peaked, you can reassemble the unit back to what it was. I suggest cleaning the excess grease/oil from all parts. This will decrease the ammount of dirt, dust and crud that the unit will pick up. Just follow the directions in the reverse order. For the full Athearn tune up, read on.

"Gimme filter, oil and lube, please..."

There are plenty of things that can be done to enhance the performance of the stock Athearn drive. What follows are several tricks, some that I've learned from various sources and some that I've come up with on my own. Tools you'll need are the screwdriver, #11 blade/handle, small needle file(s), 220 grit sandpaper, and an NMRA tarck/wheel gauge. Some Pearl Drops tooth polish will help as well (No, really!!). Here we go:


Start by marking (the ol' masking tape/pencil trick) the front and rear trucks. You won't hurt anything putting the trucks on backward, but your loco will run, well, backward (I've pulled this prank on several people with great sucess...). Gently pry the sideframes off the trucks - take note on how they came off as well, ecspecially on six axle locos. Pull the clips off of the truck assemblies - there should be a small clip on the top and a long clip on the bottom. Gently pry them off with a screwdriver and be prepared to play catch if a clip decides to go flying. Set the wheelsets aside and pull the case halves apart, notice the orientation of the gears and make note of which ones go where. At this point, I'll put all the parts, wheelsets too, in a small bowl filled with isopropyl alcohol and, using a stiff brush (an old toothbrush is perfect), scrub everything clean. If you have an NMRA track/wheel gauge, pull the wheelsets apart as well. I'll follow up with dish detergent and water. When dry, inspect all the gears for any mold flash, bad teeth, etc. If you find a bad gear, replace it. If you find any flash, CAREFULLY remove it with a small file, sandpaper or a sharp #11 blade.


And I'm happy for you, really - I am. Pearl Drops posesses, besides the minty fresh taste, a fine abrasive that works well to burnish the gear surfaces. What you'll be doing is breaking in the running gear in a half hour as opposed to a year. The results will be a smooth running loco with less noise and the motor will have to do less work as well.

Assemble the gearboxes and, before putting the gearbox halves together, fill them with the tooth polish. Assemble the loco chassis and run the unit forward and backward for about a half hour. I built a coulpe of jigs for this operation a while back, one for the four axle and one for the six axle locos. They each consist of a four or six axle frameattached to a small block of wood and a motor with leads soldered to each clip for hooking up a power pack. I'll attach the trucks to the appropriate frame, hook up power and run the chassis for 15 minutes in each direction while I work on something else.

After 30 minutes, remove the trucks, tear them down and wash everything with detergent and water. When the parts are dry, assemble the works again. This time, before assembling the case halves together, apply a SMALL ammount of grease to the gears. I've been using Labelle #106 grease for years with great sucess. Whatever you use, make sure that it's compatible with plastics.


Use the NMRA gauge. The axles will go onto the gears tight, that's what you want. DON'T ream out or enlarge the holes on the gears. Be patient and make sure that all wheelsets are in gauge. Don't forget to place the bronze bearings on the axles. A tiny drop of Labelle #102 gear oil in each bearing is plenty.

After the trucks are back together - sideframes and all, place them back on the frame. Put a small (I mean SMALL) drop of oil (once again, Labelle #102) on the top gear where the worm gear will make contact. After making sure that the thrust washers and bearings are in place on the worm gear, place it atop the gear tower and snap the cover in place. Attach the drive shafts and test run the unit. You should notice a much quieter drive.

Going All Out - The Ultimate Athearn Tune Up

So, you've been enjoying your Athearns for a while, pulled a few trains, done some switching maybe. Maybe you begin to think about just how good these things can run - "How much performance can you squeeze out of them?". Or, maybe you picked up a Kato or an Atlas loco and you've tried MUing your Athearn to it. It wasn't that much fun, was it. The following tricks will help you do both. Sure, if you have DCC, your speed tables will help compensate for dissimilar locos. But with tuning up, remotoring, etc., operation will be that much more smooth.

The Standard Athearn Motor (and electrical) Tune Up

What follows will help reduce the current draw and overall performance of any open frame Athearn motor. I'll also tell you how to hardwire the chassis, enabling better electrical contact.


Assuming that the motor is already off the chassis, pull the flywheels off each end. Sometimes this is easier said than done. Some flywheels will just twist right off while others will require a little persuasion. There are several ways, good and bad, to remove flywheels. While twisting on both, one will come loose. If the other one fails to do so, you can do one of two things. Either continue to dissassemble the motor (read below before you do...) until you can grasp the armature, then twist the other one off OR, with a pair of small serrated pliers, grasp the shaft between the motor and flywheel, and twist it off. Try not to chew up the shaft.

If the flywheels come off without a hitch, remove the top and bottom clips. BE WARNED - my modeling areas over the years are home the many small springs, either from Kadee coupler springs or Athearn motor brush springs. Remove the clips slowly, knowing that a spring WILL jump free at its most convenient time. Take the plastic motor ends, metal casing, magnets, thrust washers, clips, brushes and springs and put them in a nice, safe place.

At this point, having a Dremel tool is real handy. I like to chuck the armature/shaft assembly in the tool and, at low speed, polish the commutator (the slotted copper piece at one end of the shaft) with a small piece of 1500 grit paper. I'll follow up with a Pink Pearl eraser until it gleams. This can be done without a motor tool, it just takes more time. After polishing, clean any crud out of the slots with the tip of a #11 blade.

After that, clean up any gunk and/or additional lubrication, assemble the armature/shaft assembly, magnets, case and ends back together, putting the clips (without brushes and springs, for the moment) on to hold everything together. Take a look at the motor brushes. If your loco is fairly new, the brushes should be in good shape. If yours is more than ten years old and/or the brushes are starting to look a little worn, they are probably due for replacement. The local hobby shop, or Walthers should be able to help.

Now, once you have deemed the brushes worthy, find the brush springs. Cut approximately 1/3 of their length off, leaving - uh - 2/3 of the original spring left over. What this does is decrease the presure the spring places against the brush, creating less friction against the commutator, allowing the motor to run more efficiently. You're slow speed performance and low-end torque will definitely improve.

At this point, put the brushes (one at a time is prefered) back in, followed by the springs. Mount the motor back in the chassis, connect the drivelines and take the chassis for a test run. Waddaya think??


Most higher end locos, Kato, Atlas, P2K, etc are all hard wired for better electrical contact. No friction connections whatsoever, no place for dirt to get trapped in between, no place for oxidization to form. The standard Athearn drive can be modified easily to accomplish the same result.

Easy procedure here. Pull off the long metal clip from atop the motor and toss it. Pull the motor clip (the one holding the spring/brush in the motor) from atop the motor. Cut two pieces of small stranded wire long enough to span from the center of the motor to each metal tab mounted to each truck tower, plus an additional 1/4" or so. Strip each end back about 1/8". Tin each end with a bit of solder. Also tin each metal tab. NOW, use caution when tinning these tabs. Too much heat will distort the plastic in the trucks. I recommend using a good quality flux. My personal favorite is Tix, in fact, their solder works well for this operation too. Solder each wire to each tab, heat just enough for the wire to attach to the tab. Tin the top of the spring/brush clip and attach the other ends of wire to the clip. You might have to experiment with wire length. If in doubt, start with longer wire and cut back if necessary. You want the wire a little long so the trucks will swivel freely but not so long as to cause problems. Replace the clip back to the top of the motor and test the chassis. If the wheels are clean the chassis should now run without hesitation.

Now, if you wanna get real serious, you can attach leads dirrectly to the metal plates behind each sideframe. This procedure definitely takes more time and patience. If there's an interest, I'll list the steps.


Hmmm. Honestly, I'm in the habit of removing it and tossing it as well. It's usually the first thing that I do to an Athearn chassis: "Step #1 - Take large pliers and wrench headlight and bracket from chassis, deposit into trash...".

Sorry about that...

The headlight is easy - cut a third piece of wire long enough to go from the motor to the headlight clip, solder to the motor clip, then to the copper strip atop the bulb housing. Done.

The only thing that I really have against the Athearn lightbulb is that it casts more light into the cab than out thru the headlight.

Still Want More??

While tuning stock Athearn drives will provide well operating locomotives, to keep them running reliably you need to keep the motor and wheelsets clean, and with stock Athearn drives, you'll be doing this every 2-6 months depending on how often you operate. Admitedly, I'm the laziest person that I know, and I'd rather be detailing or running a chooch than cleaning it all the time. To that end, I repower my locos with Mashima can motors from A-line and nickle silver wheelsets from either Northwest Shortline or Jaybee. As a result, I clean wheels once a year and have never had to worry about the motors. One of my can motors is going on ten years without trouble. AND, they run stride for stride with my P2K, Atlas and Katos.

More to follow soon...

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