4×4 not working all the time

I have a Polaris xplorer 4×4 I think its a 2001 250 2 stroke air cooled. The 4×4 is not working all the time. I notice when I get up to high speed the light will turn off then come on again when I slow down. and when im going slow in a mud hole it works sometimes. it seems to always work in reverse. and if I get stuck in 2 wheel then put it in 4 wheel it works about 75% of the time. Any ideas? I saw a video a guy said it might be in the shifter. Im going to lift it up in the air tomorrow evening to test it

4×4 not working all the time

I have a Polaris xplorer 4×4 I think its a 2001 250 2 stroke air cooled. The 4×4 is not working all the time. I notice when I get up to high speed the light will turn off then come on again when I slow down. and when im going slow in a mud hole it works sometimes. it seems to always work in reverse. and if I get stuck in 2 wheel then put it in 4 wheel it works about 75% of the time. Any ideas? I saw a video a guy said it might be in the shifter. Im going to lift it up in the air tomorrow evening to test it