There seems to be a some confusion from people on other boards and especially ebay recently about the "very rare" one of 4,112 4-speed or one of 4,139 automatic 1978 Trans Ams produced. These number, while coming coming from Pontiac, are not complete production numbers and it has not been established what part of production they represent. I caution against using the 4,000 numbers as they do not represent the final numbers.
FOR THE RECORD FINAL 1978 PONTIAC PRODUCTION RECORDS ESTABLISH PONTIAC PRODUCED 34,886 W72 FIREBIRDS DURING THE 1978 MODEL YEAR. OF THOSE, 13,502 WERE 4-SPEED (12,692 TRANS AMS AND 810 FORMULAS).
Unfortunately, 1978 Trans Am and Formulas produced with the W72 Performance Package and automatic transmission is impossible to separate at this time. Pontiac production records show 75,239 Firebird Trans Am and Formulas were produced with the L78 400-cid and W72 400-cid engines and automatic transmissions. According to the early production records, 70,590 Trans Ams were produced in 1978 with automatic transmissions. Based on this number we can conclude 4,649 L78 400-cid and W72 400-cid Formulas were produced with automatic transmissions. By carefully analyzing production records, I can establish that 21,384 W72 Firebirds (Trans Am and Formula) were produced with an automatic transmission.
All 1978 individual Trans Am production numbers appear to have come from the same sources that claim only 4,112 W72 4-speeds and 4,139 automatic Trans Ams were produced, which I have verified these two to be incorrect. While some of these numbers per model (Y84,Y82,Y88) have been used and accepted in the hobby I have no way to positively say these are accurate and should be stated as "accepted" numbers or "believed to be" but not yet verified.
This information can also be found in my W72 Historic Information page on this site.
John