I have a  1991 Bonneville driver door window motor in pieces right
now......Do you mean brushes by chance? There are no plastic bushings
that you speak of, at least not in my 91 there aren't.

GM motors have two brushes that contact the armature. Mine were worn
down to the point there was not enough pressure applied to the armature,
but the culprit might end up being my express down module. Its the
original.

One of the Goodwrenches at a dealer I go to suggested disconnecting the
hot wire going into the module (there are four wires) that controls the
express down, then and see if the window motor runs.

You have to leave the wireharness connected to the module, because the
window motor power source still comes throught the module and so does
the ground. The express down module is the black box bolted the the
window motor.

Due to my schedule, I wasn't able to try this yet, but with the new
brushes I got from ACE Hardware (of all places) and this latest trick I
learned from the GM Goodwrench the motor will probably work again.

This motor was replaced in 1998. It was stopping and starting
sporatically. Same goes for lately, but I wasn't paying attention if the
express down feature was working.

Good Luck,

harryface
91 Bonneville 314,234
05 Park Avenue 72,989