why does it sound like my truck is winding down when I let off the gas? on 2000 Chevrolet S10

when im on the interstate going 60mph and I let up just a little bit the truck sounds like its winding down almost like the breaks are engaging but doesn't pull one or the other. It also slows down a lot quicker than normal like its lost power but still wants to go, and as soon as I stop the truck the sounds stops and sometimes it wont do it again until I drive home the next day. transmission is got 20k "rebuild" and the fluid is at a good level and color and no shavings! Im kinda stumped here so anything will help thanks!

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1 answer
Need more info. 2000 S10 aint enough! Body style, engine, trans. type, 4x4 what exactly do you have? Makes a big difference!