My first guess would be a belt.
If it is relatively regular, try some belt dressing/conditioner as it only cost like 2-3 dollars at Walmart. If that makes the problem go away then you know its the belt. Dressing/conditioner is only temporary though, so plan on changing the belt.
If it is relatively regular, try some belt dressing/conditioner as it only cost like 2-3 dollars at Walmart. If that makes the problem go away then you know its the belt. Dressing/conditioner is only temporary though, so plan on changing the belt.