the W-body was meant as a direct competitor to Ford's Taurus and Mercury Sable. The W-body design was originally all GM as the independent rear suspension used leafsprings while the front was updated from the A-body. Costs were kept down by using much of the same running gear as the FWD A-body the W-body replaced. The first update to the W-body chassis came in 1995 with the redesigned Lumina and Monte Carlo, which had the same front suspension as other W-bodies, but a completely unique independent rear suspension devoid of leafsprings. This redesign is referred to as Generation 1.5. Generation 2 was launched in 1997 with the redesigned Pontiac Grand Prix, Buick Regal, and Buick Century. This was a top to bottom redesign of the chassis, eliminating leafsprings once again. The W-body was then planned to be canceled in 2004, to be replaced by an extended Epsilon platform, But GM realized how profitable it still was and updated the chassis again in 2004, again starting with a redesigned Grand Prix. If you can count, that makes generation 3. The platform is still in production, but in the process of being phased out. The last surviving production W-body is the Chevrolet Impala.