Final answer:
There can be vowel shifting in irregular verbs, where the vowel sound in the present tense changes in the past tense.
Step-by-step explanation:
Yes, there can be vowel shifting in irregular verbs. In some irregular verb forms, the vowel sound in the present tense can shift or change in the past tense. For example, in the verb 'drive', the vowel sound in the present tense is pronounced as [a], but in the past tense, it is pronounced as [ai]. Another example is the verb 'drink', where the vowel sound in the present tense is [i], but in the past tense, it becomes [u]. These vowel shifts are irregular and do not follow a specific pattern.