I have recently noticed (don't remember if this happened last winter), shortly after startup, I would get on the highway and the engine is not quite up to temperature. I would be cruising at 70mph and the overdrive has not engaged yet at this point and sitting at 2500 or so rpm. It seems like its taking a few miles before it finally clicks into overdrive, or when the engine comes up to normal temperature or shortly thereafter. I don't think this happened during the warmer months. Any ideas on what could be causing this?

Totally normal and tied to ambient temp. Tranny won't shift into overdrive until tranny fluid reaches an appropriate temperature so colder it is the longer it takes. There is a mention of this in the owner's manual.

One of several reasons not to idle the vehicle in the driveway to "warm" it up. Crankup, wait for any idiot lights to go out and drive at a moderate speed until engine temp gauge shows signs of life.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs