Oh, the tragedy!!!

I can no longer claim that all my American Models locomotives have been trouble free.

While running my New Haven AC HiRail U25B's over the Christmas Holidays, they made about six orbits of my loop and began squealing like a banshee.  I removed each unit to see which one was squealing and it turned out to be both!  Arrrgh...

I immediately dug out my scale U25B's and tested them, they ran fine.

I opened one up and discovered a split gear on one of the axles.  Didn't bother checking the other trucks.  Replace one, replace them all, I figured.  I waited until after the holidays to order 8 new wheelsets to repair both locomotives.  They arrived about a week later.

So, here we go...

Here's the replacements all in a row, the insulated sides face me so I wouldn't do something stupid...

AM Gears 01

The sideframes/gearbox cover are one piece nowadays, held on by two screws.

AM Gears 02

It's a snug fit, so a little care must be taken when pulling off the cover.  This is where I found out I had one cracked gear on each truck assembly on both units and it wasn't on the traction tired set.  Interestingly, the cracked gears were all on the outside wheelsets.  Maybe something to do with the R20 curves I was running them on?  Just a thought...

AM Gears 03

Once the wheels are out, be careful not to upset the bearing springs.

AM Gears 04

Here's one of the cracked gears.  Three were cracked all the way through, the other was working its way from the axle to the gear face.  The other 4 gears looked fine, but I replaced them all.

AM Gears 05

All in all, it took about 5-6 minutes per truck to replace the geared wheels.  Most of that time was convincing the square bearings to return to their proper place.  A little grease on the gears, a drop of oil on the bearings, button them up and I was good to go.

AM Gears 06

So happy together...  I kept my Christmas loop up to test this repair and now the U-boats run like new.



Photos (6)
Original Post

Nice documentation of the repair. This was thought out in advance and organized. When I had one of my AM diesel trucks apart finessing the square bearings back in was the most time consuming. It looks like the cracks could be from material shrinkage after the gears were press fit on the axles. So far I have not seen this failure but if I hear squealing I now know where to look first.


I have recently  been hearing occasional reports about split gears on both AM ans SHS products.  It doesn't sound like an epidemic, but it has been happening elsewhere.  Northwest Short Line has a replacement gear for the SHS 2-8-0's that someone commissioned.

The interesting thing is my Scale U25B's have a lot more "mileage" under their wheels than the HiRail units.  Maybe just the luck of the draw.



I'm sorry to see this for you. It happens in G scale also. I found a set of K line trucks that I took from their GP and installed NWSL delrin gears into it. So far, it has performed perfectly. I may look for more someday.

 I also put a set into a USA trains GP engine. I never finished upgrading that engine to test it yet.

" on Sour mash and cheap wine " ??

Why go back to DCC when I have DCS!

kenv posted:

those gears are junk someone should make them out of brass.  I worked on a engine for a friend of mine same problem.  am stuff is junk!!!!!!!!!!!!!

Thank you for adding your valuable insight to this issue...

In 30 years, this is the ONE and ONLY major problem I've had with an AM locomotive and I have quite a few of them in both Scale and HiRail, to say nothing about my fleet of freight and passenger cars.

I'll still recommend AM products to anyone entering S.


I've had two American Models gears split. But then I've bought 20 of their locomotives in the last 30 years, and they have been extremely dependable. One of the great features is that it's easy to buy replacement parts and install them yourself, something that can't be said for brand new products from some other manufacturers who deliver almost a year after an announcement, supply defective products when they finally do arrive, and have no repair parts in inventory for just delivered product.  When American Models announces a product, it's available within a few months. It works right out of the box, and it works for years. If it ever does break, Ron has the parts and the suggestions for a fix.

I'm curious if anyone who has had this problem tried to contact Ron at American Models to see if replacement gears are available and if they would be provided gratis?  If the gears were defective I would think he would be accommodating.  He seems to be a reasonable guy to deal with when problems come up with his products.

It seems to me to be a very expensive fix to replace all the wheelsets rather than just pressing on new gears.  Of course I have zero experience doing either so it may be more involved than it seems. I have a fair number of AM engines but since I only have a test loop of track I doubt any have more than an hour run time on them.  Someday I expect to have a layout, and I suspect I could have this problem in the future.  If AM does not have just the gears available, I would be interested if anyone has a source of such.  I’d like to have some on hand for future repairs.

 Dean Hall

The locomotive wheelsets with gears run from $6 to $7. Trying to pull off a wheel, force on a plastic gear without breaking it, and then replacing the removed wheel with the precise gauging of the original seemed to be far more effort than just buying the entire wheel/gear set. Replacing the set is a very simple matter but does take some patience because the bearings rotate around the axles and, like frisky 2-year-old kids, refuse to go where they're told. I broke off the defective plastic gear on the bad axle and saved it for future projects.

I have bought American Models parts for detailing, upgrading, and repairing my own mistakes over 30 years. They have always had the parts available; and I suspect that for drive-train parts such as wheels, wipers, motors, and gears they keep an ample stock. These parts are common to multiple AM locomotives, which makes parts management simpler and keeps costs down.

It cost me around 42 bucks to do both locomotives.  I could have cut that cost in half by just replacing the 4 wheelsets with the broken gears, but why take the chance?

The U25B's were released 2004 and they would be out of any reasonable warranty period anyway.

A solution would be to send a gear off to North West Short Line and have them cut some new gears for replacements, (Someone did this for the SHS 2-8-0, replacements are $14.00 each) but then there's removing the wheels, removing the gear, installing the new gear and regauging the wheelsets.

My scale wheel Burlington U25B's haven't exhibited this problem, and they have much more run time than my HiRail New Haven's have.


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