I have about a 2% grade on my layout except for my helix, which has about a 2.7% grade. I also run fairly long trains that need 3-4 locos to pull it (I run non-DCC and group locos together that have matching speeds). Several loco combos glide down the helix with no problems at all even with a long train in tow. However, I have a couple of C44-9W's that can't be in the mix (at least not in the lead) because their wheels always seemed to lock up when they're pushed on the downhill run (pushed by the other locos and/or the weight of the trailing cars). This produces a pretty awful sound and I figure it can't be good for the loco either! I recently ran a test with a single C44-9W on a straight and level track, where I ran it at different speeds and then tried to push it a little with my finger. As soon as I start pushing even just a little, it's like the unit puts on the brakes... not to maintain the same speed, but like it's trying to come to a complete stop (it slows WAY down). It actually becomes pretty hard to push, until it breaks traction and starts making that horrible noise as the wheels skid along the tracks. It does this mostly in the forward direction and not so much in reverse. Anyone else ever notice this before? has anyone found a way to fix it? I figure it is a binding thing of some type. Would the Bearden technique help here? Thanks! Russ PS- It's not all of my C44-9W's that do this. I have a couple that have no problems at all. In fact, I have one that I run in the lead with 2 Atlas SD60's and a GP40 trailing, all from the original run (read rocket sleds). While it runs faster than my other C44-9W's, this particular unit runs great in the lead and does not have the braking problem at all.
This sounds very odd indeed. Have you tried the tests with one of the drive shafts removed to see if it's one shaft/truck that's causing the problem. My other thoughts would be electrical contact, and that by pushing it you are reducing the pickup which is slowing the motor - grasping at straws really though. Hope someone has a more helpful answer. Simon
It's gear lash. Ran into this problem as well with long trains on a downgrade. You are right in the sense that the weight of the cars pushing on the trailing units is bunching up against the lead unit. I solved this problem by weathering the wheels on my cars so they don't roll as free thus requiring the units to pull slightly on a downgrade. Usually a little chalk dust up in the axle cups on the trucks works. This also elimilnates most of the slinky effect with MT couplers.
I would try ordering new idler gears (and maybe double gears) from Kato and seeing if it changed anything. Regarding Bearden technique... you can not remove a bearing block from these locos because they have universal joints in the drive shafts. You might be able to adjust the u-joint position on the worm shaft so that the worm has a certain precise position and amount of play. That might have a bearing (ha, no pun intended!) on your problem. But I'm just speculating here, not speaking from experience.
