itis understandable that once a load is on it that it is quiet if it'* the SC coupler.
The way the coupler works is three pins from the nosedrive shaft go into the coupler and three other pins from the rotor pack gear go into another three holes in the coupler. The coupler is a hard plastic that takes up the place of shock and things like that.
Here is a coupler on the gear side. Coupler is green
And this is the nose drive side. We can see how they go together
The holes egg out over time and miles. While your noise is common, it'* not a threat to the motor. A coupler swap in a 92-95 requires the charger to be removed from the motor. As long as you are going that far, I'd pull the LIM and replace the gaskets as well.
Most posts you see on this forum will say that the S1 motor doesn't suffer from the gasket issue, but having seen a few in person..they do. Once in a while there will be an exception to the rule, but most are in need of being replaced.