And just for clarification:
Left and right are always determined from on the operators' seat on mobile equipment.
Your J hook adjustment is on the left side, and your spring tensioned unlocking bar is on the right side.
Put a few drops of oil on tensioner bar pivots the spring is on as it needs to not be bound up so it can put proper tension on the belt.
Also check to see tension bar indicator that flops in its slot is free to do so and you did not lock it down while replacing the mule drive pulleys.
Your mule drive pulleys should be equal distance to cross on your mule drive.