Just purchased this great looking shay from Trainworld and have just started running it with about 30 minutes on the mechanism.  I noticed a slight jerky motion when at the mid to higher speeds that is almost nu-noticeable at slow speeds.  Researched this issue on line and saw many postings about Bachmann geared engine gear problems in earlier models of the On 30 steam locomotive line-up.  Also noticed the announcement re: free replacement gear sets or repairs of same by Bachmann along the way.  My question is when were these gears improved along the way and how can I tell whether my locomotive has the improved gear sets or not?  I assume this jerky motion does not meet the performance specs of Bachmann and in my experience does not meet my expectations either.  My box is labeled for the Midwest Quarry and Mining Company with an instruction sheet that is numbered S256X-IS001.  The interior of the cab on my locomotive is "green".  Not sure if there are other markings on the locomotive to help identify what manufacturing lots my locomotive came from.  I will be contacting Trainworld re: this issue to see what they think and will consider returning it to them for replacement if they can guarantee via a test run in their store prior to shipping the replacement to me.  If not, I will probably request a full refund.   Please advise on what you think I should do about this issue.  Thanks!

Rich:  Thanks.  Took another look this morning and teared the truck down to its gearing, popped out the wheels and axles as well, looked for any grit or burrs in the gearing and could find none.  Apparently the problem is in the two vertical gears but I did not attempt to tear them apart.  Am shipping it off to Bachmann tomorrow.  My railroad will miss this unit while it is gone!  Thanks again for your suggestions.

Purchased this loco new last June 2012.  Last night I laid it on its side on my work bench to add some detailing.  When I put it back on the track only one of the power trucks would run - the other one seems to be bound up/jammed.  I took this truck off and inspected it and can find nothing obvious other than it turns about a 1/4 revolution and it jams up.  The side rods are not bent so that isn't the problem.  I use straight DC power, no DCC system.  Can anyone suggest a solution?    I like to get fixed myself before I consider mailing it in to Bachmann for a warranty repair.  I am pretty handy and have been railroad modeling for about 50 years now.