Scrape/ grind sm465 starting out.

[Awann99]

Over the last few days I’ve noticed a grind/scrape noise coming from the truck (69 1500 2wd) it sounded like a rock was stuck between the rotor and the spindle. I’ve had that happen before. Checked all the wheels and they spin fine and no sight of rocks. I jacked the truck up and put it in 1st,2nd and reverse and it did not make the noise. It make a small scrap of I applied the ebrake and then put it in gear. The noise starts when I put the truck in gear to take off and gets quieter as I increase in speed. When I shift it will become loud and then get quiet as the rpm goes up. I read some forums and maybe this could be a cracked flywheel? The clutch is disengaging. I checked it out. The u joints seem solid. The only thing I saw that was concerning was the sm465 had some slip in the output shaft. I can rotate the driveshaft an 1/8 turn each way before it stops. Not sure if that is normal. Also the drive shaft would spin when the truck was on jackstands and in neutral if the truck was running. Not sure if this is my rear end I'm hearing?
Any advise will be helpful. I am stumped. The truck drives normally. It just has this awful noise. Thank you.
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