Most of the old tractors have round disc with a tensioner under the dash console. It has been a while since I've worked on a 135 but if it has the disc the bolt in the center can be tightened. you may have to add a washer or some other type of material to create the friction.
our 165 had the splines get worn that hold the aforementioned disc to the shaft as well... solved by putting a weld spot there, I think you can access that disc without too much trouble.