I have previously performed all those steps, it didn't resolve my problem.  I put my train on a friend's track with my tw transformer the train still runs slow.  If I use his Lionel 150 watt transformer the train runs really good.  I removed cover off my transformer and checked each connector to case for resistance.  Found wires not grounded.  If I plug in the transformer and measure voltage from pin U to the metal part of case I read 10.3 volts. I  think I should read 0 volts. But I can't find any shorts.  If I had short I believe that the breaker would open.
Any thought
Thanks
Denny