Need advice about conversion 30 x 30 to 48 x 30

hello everyone , i bought my lm in 2021 ,and wants to upgrade ,
my problem is my lm is cutting ,off d 1 st cut pass ,as it goes to bigger size, projects, i checked every thing and all is square and nuts thighten,. wheels etc. my question is have anyone who went from 30 x 30 to 48 x 30 ,is it necessary to change d 2 y also ,or will d 2 y rails work ,and remain square .
i am asking ,now so i can decide how to go about my upgrade .thks ,any help is apricated