Tim,
I believe you must be talking about a 4110 tractor. If you are the shuttle linkage is done by a cable which actuates a lever on the left side of the transmission housing. You can see it if you look under the left side of your deck platform. If you can't see a problem on that end of the cable, you will have to remove the housing arround the steering column, and see if you can see a problem on the handle end of the cable. If by chance you are talking about a 4500 tractor, there are a series of linkages that go to the right side of the transmission housing. Your would have to trace the linkages and see if you find the problem some where in the linkage. If I can be of any more help, let me know. Good Luck!
Galen LaWall
Your Mahindra Tractor Dealer
Batavia, NY 14020
585-343-0770