alwaysgawn

When shifting from Drive to Rev, there's a severe knock that won't go away unless I shut off the engine, then turn it back on again. I back into my driveway and as soon as I shift, the knocking begins, regardless whether I shift into Neutral, back to Drive or stay in reverse. I had issues with a bad pinion seal and thought maybe it was due to low gear oil, but that wasn't the case. It seems to only do this when the engine is warmed up(hot). The truck runs great, shifts great, etc. The mechanic I had change the pinion seal told me there was slight noise coming from the motor and thought the Cam Phaser might be starting to go. Any suggestions/ideas?