The triphtong iau which we already have in Old Gutnish remains as iau in Modern Gutnish. Though in some circumstances it has fallen to au and that is after r. In the modern gutnish orthography (www.malsaudin.com) the old spelling is preserved though.
Old Gutnish Modern Gutnish English
Briaust Braust Breast
Hiaul Hiaul Wheel
Iaul Iaul Christmas
Liaus Liaus Candle
Diaupr Diaupr Deep (masc. form)
In braust the r-sound is about the same as in Standard Swedish or other Scandinavian languages or German. Though in Diaupr the r-sound is like an american r. So in Gutnish there are two sounds. The american sounding r is when words either ends with an r or when it is followed by a consonant.
Today most people put in a vowel between p and r in diaupr so it is pronounced diaupar or diaupur or diaupor.
If we compare with Swedish, the spelling is djup but the pronounciation is iup.
Hiaul and iaul tends to be pronounced the same way today, without the h-sound. Perhaps influenced by Swedish which is spelled like hjul (wheel) and jul (Christmas). Both are pronounced the same way (about ‘iul’).
The same goes for Liaus. A hundred years ago it was pronounced as spelled here, but today probably all people say ‘iaus’.