I have a 3050 with 328,000 copies on it. The machine works just fine from all the paper trays but when you use the bypass it makes a horrible grinding noise and jams. Usually you have to open the front cover, turn the green knob and then open the left side cover and remove the jam. I swapped out the bypass unit with a brand new one from a showroom machine but no luck. I also swapped out the middle feed unit 302GR93210 and the feed unit that just slides into place from the left hand side of the machine. I also swapped out the drive belt 2BL22590. No luck so far. I can't see any bad gears or belts so I am open to suggestions...

I had a similar noise, had to replaced Vertical transport assy. it didn't show bad gears but noise went away. ML.

MLTech is right. I had a similar problem on a 3035 machine. They are designed about the same in this area. Check this post out in regards to your issue. http://dnet-km.com/eve/forums/...=273106891#273106891

verticle feed assy has a broken gear in it when you take that assy out you should service the clutches in that section to i have seen alot of the gears brake it happens when the bypass feeds multiple sheets in it and binds and brakes off teeth off the gears

I took a vertical feed assembly out of a brand new machine we have in the showroom and tried it my problem machine. It did not make any difference what so ever.

is the paper making it to the bypass drawer in the middle of the machine? or is it stopping at the bypass tray when it lifts and pulls? i've had the mylar between the two sections going "backwards" preventing paper from going thru. dont know if you have checked that or not.

Check the drive belts in the rear of machine they provide drive to the paper pick up and toner drive systems. There may be teeth missing.