Zetor 5745 4wd problems

Hello everyone. This is my first post.
I discovered this site while trying to find a solution to my tractor problem.
I have a 5745 zetor and the problem I am having is my lever to put it into 4wd is engaged but I am not getting drive in the front wheels. I have basically left it in 4wd for about 7 years and it's been good as gold up until now.
Hopefully some of you have ideas on what could be the problem?
Thank you for any help.

Hi
First of its the seven years runing thats cosing your problem, thise 4wds are not suted for continues drive, the windupp have most likly striped the dogcluths in your droppbox or the innshaft inn the frontaxel is sheared of.
Bjarne