These locomotives are known to run slowly. They are geared that way -- not just this Hudson, but most of them. That being said, with my 785 Hudson, it literally took about 10 hours of running for it to really loosen up. Now it runs really very well. Not super fast, but nice and smooth. Pulls six Lionel aluminum cars without any issues at an appropriate speed (using a 180w brick). It's actually a perfect loco for the kids to use because it never derails, and while it smokes and has a whistle, it doesn't go fast enough to tumble off the tracks generally (although at high speeds, it can get close).
If you are satisfied that you have done everything maintenance-wise, there is a way to properly shim up the motor and maybe you haven't done that correctly? I don't know, but it is also possible. Finally, the motor can be replaced if that is the issue instead of the driveline.
It's probably a bit taboo over here, but do you know that other train magazine? About 15 years ago, they did an article on tuning up Hudsons. It is likely still available if you call them or email them.
Final thought is that depending upon where you are, you can find a good tech. On this forum, GGG and GRJ are aces. If you can ship or are near Maryland, I have used Frank Vacek with great results. Frank used to work for Williams, pre-Bachman, and he is an ace with the postwar equipment and the newer stuff too. If interested, I can send you his contact information.
HTH.
PS: Marty is not wrong about transformer. I appreciate that not everyone has the bucks for a ZW-L. That being said, you should test your ZW for output. I thought the ZW was the end-all be-all until I started using more modern power bricks. The trains do run better and more consistently. If it is not right, you can find another, good used ZW or look here on the forum for a used MTH Z4000. All that being said, if your ZW is OK, a 783 should run just fine with it.
