Ams ordered with the 4-speed Borg Warner Super T-10 manual transmission received the W72 T/A 6.6 engine. There are no manual transmission equipped Trans Ams that came factory with the standard L78 400 motor in 1977-79. The W72 Performance Package also included an upgrade to the rear differential ratio, setting the rear gear ratio to 3.23 for all 1977 and 1979 W72 Firebirds, with the exception being 3.42 for 4-speed equipped W72 Firebirds in 1978 only. All W72 equipped Trans Ams featured the "T/A 6.6" shaker decal. A common misconception made by enthusiasts was the notion that all Pontiac engine equipped Trans Ams featured the "T/A 6.6" decal on the shaker, however, it was exclusive to the W72 engine that was featured on less than half of all Trans Ams made during this period. All L78 Pontiac 400 equipped cars received the same shaker decal as the L80 Oldsmobile 403, being "6.6 LITRE". This may have been propagated by the only authorized company that is licensed to reproduce these decals not including the "6.6 LITRE" in the Trans Am decal kits, and only including "T/A 6.6" with no extra cost. For the 1978 model year, Pontiac re-incorporated the earlier thicker cast cast engine block denoted by the cast number 418988 and a "XX" cast into the side of the block. The earlier 1975-78 blocks had metal shaved from the journals and bottom end as well as a decrease in the nickel content of the block in an attempt to decrease the overall weight of the vehicle to help alleviate emissions and cost. The camshaft was also revised to have a slightly higher duration, the carburettor jets tuned and a dual exhaust was implemented allowing the power to increase to at 4000 rpm and of torque at 2800 rpm. By mid-1978, the W72 could no longer be ordered in conjunction with the MX1 3-speed Turbo-Hydramatic 350 automatic transmission, and could only be ordered with the 4-speed manual transmission. By 1979, Pontiac was no longer allowed to produce the 400 engine as emissions further tightened. Pontiac had prepared for the forthcoming cancellation of the venerable 400 by producing large volumes of the stronger cast "XX" 400 blocks in 1977 that were assembled in 1978, and stockpiled at a warehouse by the assembly plant for later use. The 1979 Firebird model line was the last year for the Pontiac 400, and by this