needs to shift on 2007 Chevrolet Silverado 2500 HD

does anyone else have the feeling that their truck could use another gear mine is always holding back as soon as i let off the gas it slows down right away it doesnt coast at all my foot is always on the gas i only get 10 to 13 miles per gallon i got that much when i had mt 2500 avalanche with i think it was an 8.1 litre this is ridiculous that they would both get the same

Asked by for the 2007 Chevrolet Silverado 2500 HD
It could be that your torque converter is never engaging. Definitely would be worth checking into, as your concerns do seem abnormal.
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is it shifting 3times