R62 grinding up corn

Looking for some advice, Last year I ran 4 mph with a 6 row head and had some rotor loss, this year If I go over 2mph it grinds the cob and the corn . I had in 2 reverse bars took them out and no change . I am wondering if I need new helical bars or what been anywhere from 280 to 400 on the rotor speed and 300 is the best but is still terrible. Concave been from 5 to 12 and not much change I have tried everything I can think of but it is like the rotor won't kick the material out it just wants to grind it up.

Corn is about 22% I have taken corn at 35% and done a good job yes the gearbox has a shift low gear in corn . I have run Gleaners all my life but something just is not right and seems to be getting worse by the day.

If the processor has 1500 hrs on it, the helical bars are shot. With a flashlite look at the helical bar height on the front side of the cage immediately to the left of the rear feed chain opening. That is where the helical wear will be the greatest. Now, look elsewhere thru the cage for comparison. 3/8" tall is new spec.  Two reverse bars need to be left on the rotor on the discharge end.  You don't say what model year the machine is, but prior to 1996 I always pulled every other wire out of the rear half of the main concave and also the separator grate to eliminate cob plugging of them. Plugged grates promote rotor loss and grain damage !!

You likely know this, but slowing the rotor down will increase your cob breakage on a Gleaner. I would guess Dr has hit the nail on the head to your problem.  I did have one variety some years ago i could never stop the  cob breakage, just quit planting t , lol!