After about an hour on the hwy on deceleration a very strange noise filled the cab for about a second and a half. Sounded like a canvas zipper the rims picked up then the truck goes back into normal mode. Moderate acceleration seems normal without slipping. But as soon as you let off on the accelerator the zipper sound fills the cab and the rims go up for a brief moment then back to normal. This all started around 20 miles from the house and toward the end of our trip became more frequent. Dropped the transmission into manual and limited it to 5th gear. Eventually it would do that as well in 5th gear. Still checking this seems to only happen deceleration. No leaks, the fluid level is good the fluid is red in color (dark) doesn't seem to smell smoky or burnt. Any advice would be greatly appreciated