The /ʊ/ vowel is spelled <oo>, <u>, and <oul> in should. The /ɪə/ diphthong is spelled <eer>, <ear> or <eir> in weird.
This is a contrast between a short vowel and a diphthong, widely separated in the mouth. It creates no problems.
good geared pud peered should sheared stood steered wood weird woody weirdie