Please help

I'm having extreme trouble with this challenge. I've been trying several different approaches but get stuck on the vowel triplets. The following is what I'm currently working with.

VOWELS = "aeiouy"

def translate(phrase):
    translated = ''
    for letter in phrase:
        if letter not in VOWELS:
            translated += letter
        if letter in VOWELS:
            first = phrase.index(letter)
            end = first + 3
            if letter * 3 == phrase[first:end]:
                translated += letter
            else:
                translated.replace(letter, '')
    return translated

The issue I get is that it either appends every letter to the new string, or it will only append just the consonants. Any hints are appreciated, I've spent about 4 hours on this one challenge. I tried to learn regex for this problem but that ended in a dumpster fire.