This is the Lionel 6-84945 PRSL E6 Atlantic, it's a project that has been months in the making. 
I traded for this a few months ago, I gave him a working TMCC PRSL E6 Atlantic. The previous owner who obviously wasn't a train person, chopped the rods up because it "wasn't running right". Well, the reason it wasn't running right was the motor was shot. When I went to look for parts, you can't buy either the motor or the running gear parts! Add to that the cylinders were all beat up for some reason, and it was kind of a mess. OTOH, shell, tender, electronics and smoke units were all fine. So, the quest for parts started.
I got a scrap conventional Atlantic for the motor and hopefully the drive rods & running gear. Well, the rods and running gear didn't work on this locomotive, even though Lionel claimed they were the same parts! However the motor did work, and I also got the cylinders and a couple other small parts to start the assembly process. A friend Pat, aka @harmonyards, said he had some MTH rods and running gear that could be adapted, so I sent the chassis down to him. All was well, that looks great, probably better than the Lionel stuff. Sadly, on the return trip, the motor got whacked and the shaft was bent! RATS! Pat came to the rescue again and moved the worm gear, to a new motor. Got that and installed it. I figured I was at home base. Oddly, although it ran pretty well, it seemed to start off with a bigger speed step and it only had 2-chuffs/rev!
After more head scratching, it was finally determined that I had a 2-lead worm instead of the correct 1-lead worm gear. The angle of threads on the worm was indeed different, it's a wonder it ran fine in the locomotive! Keep in mind that Lionel listed the motor as the same out of stock Atlantic motor, obviously that was not correct. OK, I had the original worm from the dead Legacy motor. Before it hit the can, I had cut the shaft and then saved the worm. I sent that one back to Pat, and he equipped it with a set screw and slightly milled out the hole, just enough for a nice and easy friction fit on the shaft. Slipped that worm on and what do you know, the locomotive has 4-chuffs and runs like a Legacy locomotive! I still wonder if it was worth the effort, but at least it's finally a working locomotive again!
