I was given a New Acera Rear Mech from Trek under warranty . It took so long to get it out of them . I purchased a Deore for My Verve 3 Disc .so I could continue riding this summer . Since I have no intention of taking the Deore off my Verve 3 . Can I use this Acera on a Trek Verve 2 with 8 speeds that currently has an Altus RD ? I'm assuming I can . Would I need a different chain ? Thanks