My FC-BT NS #661 Baldwin ran fine for awhile and then one day I took it off the shelf and it started making a gear gnashing or grinding noise from the rear truck. Upon closer inspection I discovered that only one of the two machine screws on the front truck that hold the motor in place was snug and the other screw was completely loose. The front truck ran fine. The rear truck, however, had the same screw snug, but the other one was only half loose (see photos below, Ls=loose, Tt=tight or snug). When I completely loosened that screw on the rear truck it too ran fine. As I tightened that screw on either truck the gear noise came back. In fact, the more I turned that screw in the slower the motor would run until if I snugged it down the motor would completely stop. I contacted Dean at Lionel Customer Service. He promptly inspected some engines and found the same thing to be true there as well. Apparently the worm is not installed far enough onto the armature shaft for both screws to be snugged. The work around he came up with, tested, and recommended is to install two 6408639114 (0.114" ID x 0.180" OD x .0145" THK) washers between the motor mount or base plate and the top of the truck. Dean offered to do that on my engine or I could. I appreciated his offer, but did the work on both trucks of my engine and now both motor screws can be snugged on both trucks and the engine runs fine -- arguably better than ever. I installed the washers between the motor and the top surface of the motor mount or base plate (see photo below). Apparently either location of the washers works and serves the same purpose (to raise the worm up a little bit). Dean passed this discovery onto engineering and the issue will be addressed in future production runs.
PLEASE don't go buy mass quantities of this washer just to hoard them or sell them back at a higher price to others that need them. I've seen this done with other Lionel parts found to repair or enhance an engine's performance to the point they're suddenly out of stock. That isn't fair to the rest of us in the hobby. Thank you.
PS I tried to gently nudge the worm a bit further onto the armature shaft with an arbor press, and then light hammer (with the opposite end of the shaft supported in both cases) and it did not budge, so I think two washers is the answer. I also applied a bit of Lubriplate 630-AA multi-purpose lithium grease to both worms before re-installation. They both looked pretty dry. Runs well.
Hope this helps, maybe with FC-BT GP7's as well as BLW's.
Dave
