There's several tips in your mower manual. Like this one below.
Another tip
Maybe the above was not directly related. Just mentioning OP might find a resolution in the mower manual again.
Most likely something is not aligned proper, someone might of hit a 350 Chevy engine block with the mower or normal wear and tear (bearings).
Interactive Manual
manuals.toro.com
- Brush or blow out debris from the inside of the shield and around all the parts.
- Hold a 0.25 mm (0.010 inch) feeler gauge, a piece of paper, or a note card against the wall and slide it down behind the belt tension spring.
Note: If there is a visible gap between the gauge and the spring, tighten the adjusting bolt and the nut until the paper barely slides freely in and out of the gap (Figure 36).
Another tip
- Important: Do not overtighten the adjusting bolt. This could damage the blade-drive belt.
- Install the blade-drive system cover that you previously removed.
Maybe the above was not directly related. Just mentioning OP might find a resolution in the mower manual again.
Most likely something is not aligned proper, someone might of hit a 350 Chevy engine block with the mower or normal wear and tear (bearings).