If they truly have only 40K on them, they should not be shot. I only start thinking of replacing them at 100K or if they start leaking....that said in recent years the bilstetins I have bought for my dodge truck only seem to last about 50K which is double the other brands available.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.