If the transmission delays initial gear engagement after being parked overnight or longer, it may be due to a suspect transmission cooler return filter. If the transmission was recently serviced and the part number for the cooler return filter contains an "AB" suffix at the end, a new filter should be installed.Google+
Car Problem Reports
Dodge Ram 2500 Replace Transmission Cooler Return Filter if it Has "AB" Suffix At End
Dodge Ram 2500 Problem
Drive Train Affected: 2WD
Visitor, 2005 Dodge Ram 2500, 2WD, 110,000 mi
My truck does exactly this. I put it in gear after it has been parked overnight and it takes a few seconds to engage in gear. I recently had my transmission replaced.