I have a Yukon XL 5.3 w/203k miles and am experiencing a situation where when you do a steady cruise with the engine revving around 1500-2500 rpms, you can see the tach going up and down about 100 rpms. Around idle or high revs there this doesn't appear to be happening. It doesn't feel like it is shifting in and out of gear, but might be. If I shift to the transmission to different gears or tow mode, I experience the same thing around those rpms. There is no detectable slipping into gears or at takeoff, etc.
Any idea of what this might be?
Any idea of what this might be?
