Different era, but my 1992 Bronco's dash will pop (not as loud as you described, but loud, and will startle you) when the defrost is on and it warms up or when it's hot out and the A/C cools it down.
I don't know what it is. First time I heard it I thought the glass cracked.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona