Did you ever find the source of the chirp under light acceleration? I am having a similar sound in my 2025 2500 with 3000 miles, with light acceleration between 30-40 mph and only when the engine has a little bit of load. I thought it was coming from the rear end, dealer said they didn't hear it, then after a second drive they said it was my truck cap whistling... but it is a chirp that clearly only happens under light engine load. I added fluid to the rear diff as it was a bit over half a quart low (same dealer said level was fine, took over a half quart to bring it up to 1/2" below the fill threads) it still made the noise after that.
