Polyurethane bushings are designed for a performance like ride. Polyurethane may squeak if not properly lubricated. You should use a lubricate will not wash away. Once the lubricate is washed out or contaminated from road grime the lubricate will no longer be effective. You will need to re-lubricate.

Rubber bushings are designed for the "street" use only vehicle. They provide a more factory like ride. These bushings do not need to be lubricated, but will not provide you with that "tight" suspension feel.

ALWAYS CHECK FOR SUSPENSION CLEARANCE.

Modifying any suspension component may change other part clearances and cause binding or interferences.  After installing any of Ingalls' products, the suspension must be checked for binds or interference between all components, other arms and the chassis. Be sure that all control arms, struts and steering ends move freely through the full movement of the suspension (springs may need to be removed to fully check component travel). Installing any Ingalls product on a modified vehicle (lowered or raised) from the original factory design requires a detailed check of all suspension components and their movements. Ingalls recommends that a trained technician install and adjust all products.