Loose front truck MTH PRR 4-6-0

Just going from usual reasons here since I don't have your excat model loco, but I'd check for a loose mounting screw, there should be a spring between the truck and the frame, may have fallen out, or needs gently strecthed. 

Thanks for your prompt reply.  I can't find any loose piece on the track or board.  I'll look to see if there is a specific model number for the locomotive itself.  It is from RTR MTH set, 30-4215-1 with Proto sound 3.0.  It's PRR # 7080 from the lettering and numbering of the locomotive.  I'll also get a photo or two up ASAP. Thanks

Some pictures that may help clarify the situation.  Does MTH have any exploded parts views of their locos so I could see if anything might have fallen off?

Thanks

First check the arm extending off of the back of the pilot truck to the frame of the locomotive. There is a screw attaching the arm to the locomotive that may have come loose. Moreover, there is a large wash that may have slipped through the arm allowing the pilot truck too much freedom. The washer may have slipped through the arm when you pickup and handle the locomotive.

Here is a link to the operator's manual for your set.

http://www.mthtrains.com/sites...tion/30rtr17771i.pdf

On Page 36 there is a sketch and photo of the pilot truck you can use for guidance.

If the problem persists, try this.

Increase the down force on the pilot truck by installing some washers to compress the spring above the truck. Try two washers to start, one above and one below the spring. I am guessing that #8 washers will fit. You can access the spring by removing a snap ring under the pilot truck. Put a film of grease on the washers to reduce friction.

I do not recommend that you stretch the spring as it will affect the its elasticity, and if you over do it, the stretch cannot be undone to get the spring back to its original shape. Also, do not put the washers under the pilot truck as this will raise the it relative to the rails.

The parts manual attached (icon below) is for an earlier Rail King 4-6-0 (30-4046-1), and the pilot truck is typical. The part numbers may not be the same for your locomotive, but the configuration is.

It looks like everything is in place.  The front truck DOES have a lot of articulation in every direction, but I've never found it to be a problem.  Were I in your shoes, I'd be examining my trackwork for problems that might be leading to your derailments.

Thanks to you all for your helpful suggestions.  Bobby Osage, thanks so much for the manual and the parts list with exploded diagram.  Those pdf's are great!  The manual that was packaged with my RTR set had a sparse 28 pages.  Tomorrow I will work on surveying the track carefully and enhance the leveling and support of the 4x8 board.

Thanks again.

Be sure there is grease on the truck mount plate at swivel arm arc. From the pictures where it looks scratched, it could use a coating of grease. this will help the truck from derailing. And be sure to oil the axles.

Thank you...I did oil the axles and where that scratch was I also put a few drops of Hob-E-Lube ultralight oil (HL 653) but as you say some grease on the scratched area would be better...can you recommend a grease brand or consistency that would be good for this?  The front truck did track better after oiling the axles.

I've been able to get excellent tracking around my layout (an oval with a bypass track) in one direction through several O-31 switches BUT when I try to back through this same layout in reverse the tender de-rails at most of the switches (even after I oiled the axles of the tender).