differecnes between case 621 and 621b

I just bought a case 621 sn 00271##

I have found a service manual on cd for a 621b what are the differences


what are any issues with this loader it seems real good and fight I checked the pivot and it looks good no play bushings look good and all take grease

oils look like it was serviced the only issue I have is the steering column lock needs some attention and it needs lights

I know it has a Cummins engine but besides that I would like to know what trans it has ect any thing would help

thanks all