C850D leaves trails on images generally after the 2nd or third image. These are copies and internal prints. The trails are like a poor cleaning blade and at times getting a residual image elsewhere on the page with 11 x 8.5 and 11 x 17 prints. When panic stopping, found residuals and trails on transfer drum assy but not on drum assy. Have replaced transfer drum assy and transfer cleaning assy and transfer belt assy with new kit assy's. Yesterday, replaced the drive assy for drum and transfer drum assy and cleaning assy and still have same problem. When I take the male dog off the transfer cleaning assy and run the machine, this mimics the problem exactly. Put the dog back on and it cleans once or twice then it's over. Clutch and motors check out via sim. With all the goodies replaced, it should have corrected the problem. Another weird thing is that most of the time it does not include black. Only the colors. But color drive also replaced in same drive pack as transfer drum and drum drive.

Did you replace the "Clutch SP CAM". It's attached to the back of transport bed ass'y. It's easy to replace. It may click through SIMs but it can cause imaging and jamming problems.

Unfortunately I have many 4008s and I always carry this with me.

16. Cleaning brush unit drive clutch ...................................................... Controls driving the cleaning brush unit. Page 2-2-7 of the service manual.

If you don't have a new one you can take this one apart, clean & relube and that will cure the problem.

cleaned out the clutch today and swapped out the pivot clutch that drives the cleaning unit against and away from the transfer drum and problem went away. That assembly gives you some very bizarre copy quality issues when the clutches are not working. One clutch is a standard electromagnetic clutch, the other is the old style wrap spring clutch. I did find a Q and A regarding a mylar wrap on the electromagnetic clutch that extends further toward the drive gear to keep dirt and grease from entering the clutch. Thanks everyone.