1995 3500 stuck in second gear

I have a 1995 3500 that is stuck in second gear. I've read some of the post and my plug on the side is wet with fluid. I've just replaced it a few days ago and it shift for a day and stop. I also hot wired the shift fuse and it is still in second gear. So I am guessing it's the plug.

-I have a 95 2500 that did the same thing. Replaced the shift solnoids first but that did not work. Had to have the trans rebuild.
This problem started after I tried to pull out a stump using reverse.
Trans man told me never pull like that in reverse the high torque broke some drum or something in the trans.
Never heard that before but I guess he knows more than me