Ok, See you did move this question to "Wheel Loaders" and answered at least one of my questions but I will copy and past them all here:
What model is this machine? Might help with more ideas. "ANSWERED!"
Does it still seem to want to go forwards if in say first gear?
When put in reverse does it sound like it is under a load while trying to back up or does engine rev-up like it is in neutral?
Does this machine, as you gave no real info one has to guess, have a drive shaft between the converter and transmission?
If so does it spin when engine is running in neutral, in a forward gear or reverse?
Lots of things that might be able to tell if there in person but without asking lots of questions and getting good detailed answers it will be just a bunch of wild guesses!