My TC40DA (not supersteer) has a similar problem with 4-wheel drive selector, but my lever is "stuck" disengaged. It has been quite hard to engage the 4wd lever since I bought it second-hand, but just got to the point that the lever just won't move at all. I really miss the 4wd and I hope to get to check the linkages (external) next week when I get to the property where the tractor is. If I see anything on mine that may appear to be helpful for your issue, I'll try to post back as soon as I can -- but, I warn you in advance, it often takes me way longer to get back to the Forum than I would like. Best of luck to you.