Could anybody shed some light on this for me please? My 08 DTS has 128,000 miles on it and is just about flawless. The engine revs at 3000 RPM's when going 60 mph. There is no difference in 3rd and D when shifting my automatic transmission. What needs to be done what can be done? There is no engine light on nothing to indicate a problem I'm puzzled. Is the dealer the best place to have this addressed?