I have about a dozen of the first run Bachmann C40-8's from the 90's,the first ones they did,including the first wide cabs..They ran half decent when I first got them,but eventually,they got so slow they just ended up taking up[wasting..] shelf space.Made no sense,since basically,they're nearly the same chassis/motor as my SD45's,and they run good..
I was gonna buy motors for them,but decided to look at the motors that were in them first.I took them apart and threw it all in a pile.Every motor had a solid plug of brush material between the comm segments,so I started out by cleaning out the segments,and totally degreasing the motors.I noticed that,in all their wisdom,Bachmann had put a plate over the brush/comm area,so,before I cleaned the frame halves,I used Mr. Dremel to hack out the plate,so I could easily access the comm to clean it without disassembling the entire loco.Don't cut out the bar that holds the motor in!!! I brushed the frame halves off with a small brass brush,and lightly sprayed them with WD40,wiped them off,and cleaned up the rest with a Q-Tip. I also did one other mod.The brass tabs that hold in the brushes are stupid.One wrong move putting in the motor,and the contact to the frame is compromised.It makes it a little tough to get the motor back in,but I broke those tabs off,and stretched the brush spring so that they contact directly on the frame.The top one is easy,but the bottom one needs to be slid under the frame tab with a thin,flat probe.
The motors seemed to run fine after the cleaning,so I REALLY lightly oiled one,and reassembled one chassis.STILL ran like a turtle!! This really puzzled me,since the motors ran great before I put it together.I ran the chassis with a 12V battery,same one I used to test the motor in the chassis.The RPM's were half what they were without the trucks...
I pulled the trucks apart,and found the problem.The three main white gears were slightly dragging!! If you turned them,they felt fine,but the cumulative effect of six of them dragging was enough to nearly grind it to a halt.Turned out to be a few problems.Bachmann used heavy white grease on the trucks.The large flat contact surfaces of the brass contact strips against the backs of the wheels,plus the drag of the gears on the inside of the trucks because of the grease,made it as if you were running it in molasses.Even though it felt fine if you turned it by hand,when it runs,it robs so much power from the already crappy motor,none of mine would do more than 20 SMPH.I completely disassembled the trucks except for the worms,cleaned all the lube,and I used a bit just slightly larger than the gear holes to ream them out a bit.I put the trucks back together totally DRY,except for the worm bearings,and they only got a speck of gear oil..ANY oil on the contact strips will slow it right down!!Also,try to get the contact strips down to minimum spring pressure,any drag in these kills them. I put the first test loco back together and ran it..WAY better,faster than the fastest one I ever saw.I did three so far,all were tremendously improved.This will probably help any Bachmann loco,especially six axles..
Also,an observation.There are two different wheelsets on these locos.Plated,and blackened brass.Every single plated set I have had one wheel loose on it in the gear,all the blackened sets were fine...
