Bizhub C500 problem - cannot do face down printing

Hello,

So I recently purchased a c500 (well, Ikon CPP500 but same thing), paid the guy who sold it to me to do some repairs on it and of course, he ran away with my money.

So before he ran away, he told me the unit cannot do face down printing because some gear needed changing. I cannot do folding because I need face down printing to do that. Basically if I try to do face down printing, the paper jams just before it is transfered to the finisher (I think it is called the intermediate transfer unit, just before it exits that). Can anyone tell me the part and part number that needs changing in order to fix this? When I got the printer, a gear was taken out of the printer. The gear can turn in one direction, but does not turn the other way. When I looked inside the transfer unit, it has one of these gears. So one is taken out of the printer, one is installed in the printer. Any ideas? You would be saving life.