Well my shindy t-25 i got cheap is running pretty good right now. But i kept on getting this nusicance vibration, so i dug in to try and find what i finally found it was the gear box. When i took loose the guard the gear box could turn on the shaft. Either the gear box is off a bigger trimmer, or the shaft has been changed to a smaller and the old box reused, anyway i took a coke can cut off the ends then cut it to where it wrapped around the shaft, slid the box back on and retightened and it was rock solid.(basically made a bushing so the box fits the shaft tight) Put the guard back on and the vib seems to be gone, it was getting late so i didnt run it too long. So does anybody know why shindy uses different size shafts??? And any idea if my fix will work??