Thump & Grind

My Press extruder had been working pretty well, for ABS anyhow. I'd been through all the drive wheel tightening, Vref tweaking, fan flipping, etc. and all was good. No longer.

I started having extruder troubles. Figuring it for a clogged nozzle, i soaked the nozzle and heat break and cleaned them out. After reassembly, still no go. Rechecked drive wheel alignment, drive wheel grooves, heat break clearance. Cleared out a few stray bits of filament from the fins of the extruder, dried the filament (and tried a differnt roll). Still no go. Tried bumping the temperature, and the changes in smell and print quality make me think the reading is roughly the same as before problems. Ran a fine sewing needle into the nozzle to check for clogs. Tried some cool retractions to pull the melt pool out of the nozzle.

What I get is occasional thumping, until it strips the filament. The print gets gaps consistent with the thumps. Letting the extruder cool then opening, there is no bulge above the heat break nor buckling filament .

Any ideas here?

Given the split in fails between thumping and stripping, it seems like there's plenty of torque & grip. Yet no buckling below the drive wheel. A clue? (Or maybe not)

The only thing I've found odd is that the idler wheel is grinding a groove in the extruder body. I don't know if that's causing enough drag to spoil things. Has anyone else seen this? The lever on my extruder has never sat squarely, and I think this is letting the bearing drag.

[Edit - drat -  posted to wrong discussion group - dunno how to fix that]