I own a 2005 Toyota Tundra 4.7L, automatic transmission, V-8 double cab with approx. 76,000 miles on it. Lately the transmission has been shifting in and out of overdrive by itself. I always drive in overdrive and lately whenever I shift from park to drive or reverse the overdrive turns itself off or when I drive down the street the overdrive will turn off by itself. I usually just jiggle the transmission shifter handle or tap on the overdrive on/off button on the end of the shifter and it will go back into overdrive again, but this will happen several times during any trip. I'm thinking the problem is in the overdrive on/off button on the end of the shift handle or possibly in the handle itself. I'm guessing that something isn't making a good contact thus it's shifting in and out of overdrive. Advice/Opinions???