(Detroit-WWJ) A lawsuit filed in Detroit claims General Motors fixed a defective part on Chevrolet Impala police cruisers but did not correct the same problem in thousands of other Impalas.

According to the class-action suit, 2007 and ’08 model-year Impala sedans have defective spindle rods, which connect the car’s suspension to the rear wheels. The defect can make the tires wear faster.

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Plaintiffs claim that GM instructed dealers to replace the spindle rods and tires on affected police vehicles but did not offer the same remedy to civilian Impala owners.

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General Motors sold some 423 thousand Impalas during the 2007 and ’08 model years.

There was no immediate comment from GM.

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(Copyright 2011 WWJ Newsradio 950. All Rights Reserved. The Associated Press Contributed To This Story.)