case ih 800 series corn head questions

Hi all, we recently purchased an 12 row 800 series corn head and have some questions on bearing/bushing play. The gear that drives the gathering chains has some play in the gear box and will come up and down maybe a 1/4"-1/2" and makes the chain slap around on the bottom end. Are they supposed to be able to move that much or should they be rigid inside? We've pulled one gear out and found some wear on a brass bushing/bearing and were wondering if a new one will solve this slop?