We seem to have two threads going on that are very similar, but here's my "solution" to my UP Geep's poor performance. I went to the auto part store to find those stick-on weights. They had them but they're no longer made of lead (Pb). Are they afraid we're going to eat them or something? Oh well. They're still heavy and have adhesive on them (they're iron, BTW). The ones I got are in .25 oz. increments. I added a total of 1.5 oz. and it made a difference. I tested it on my layout, and it pulled my 7 cars up the grade with no wheel slipping. On level track, I'm sure more can be pulled. I also cleaned the track and wheels, but they were fairly clean to begin with. So here's my weights in place.
They had to be staggered like this to clear the shell. It was a tight fit, but they fit nicely (notice the pencil marks on the deck). I couldn't add any weights in the front of the motor due to the wires for the electro-coupler. By the way, in the process, I broke a wire leading to the coupler, but was able to re-solder it in place after carefully removing the Mylar tape surrounding the coil. I know, I know. I voided the warranty, but at this point, it doesn't matter any more. In the process, I also mixed up a batch of Testor's Model Master grey paint to try to match the UP grey so I can paint the pilots. They aren't a perfect match, but they're look better than black. If I find a better match, I'll repaint them, but for now, it's fine. I've tried matching Lionel colors in the past, and they're difficult to match, but I used to use Floquil paints. They're no longer available, so I use whatever I can find, but NO KINDERGARTEN WATER BASED FINGER PAINTS!