Originally Posted by TippnOver
i was going 60 on the way home tonite...and i let off the gas...and about 1 second after i let off, my truck dropped from 2k RPM to about 1.3kRPM....along with 2 rather loud bellows from the turn down exhaust...
is this normal downshifting or is something up?
i repeated this several time and each time it did the exact same thing....
As per previous comments, your truck upshifted, which it will do when you back off the gas after accelerating to a higher speed like that. It sounds like you went into overdrive and your torque converter locked up in quick succession.
Why would your engine "bellow"? Not sure I understand that phenomena in this context. The exhaust note should drop a bit in pitch as the RPM drops. It's possible that you have a "resonance" in your exhaust system, which is VERY common, and that you hit that resonance at the RPM range you dropped into.