The 77 Trans AM was built before ratings were required.
The 455 cid engine got 11 or 12 when run moderately hard and could get 18 mpg when run gently.
Standard trans, 25/31 Automatic trans, 23/30
44,704 total production of 1977 trans ams.
It depends on the size of the motor!! 231ci to 403ci..............
Mine gets 23 - 25 mpg (2.4L 4 cyl with auto trans)
A 4 wheel drive with auto trans gets 16 mpg highway 12 mpg city. The manual trans gets 17 and 12.
A bigger trans wouldn't change anything in fact it would weigh more and probably cause you to lose mpg. If the present trans doesn't have an overdrive, replacing it with one that does would increase mpg.
15 MPG city / 23 MPG highway according to www . fuel economy . gov ( no spaces )
I just changed oil and oil filter on my 77 Trans Am, It went about 7 litres. 400 CID Pontiac engine.
2005 XC90: 19 mpg in-town; 24-26 mpg highway
Mine gets 23 - 25 mpg (2.4L 4 cyl auto trans)
77 Trans Am SE.
The mystique is listed as 18 mpg city, 28 mpg highway. (2.5 L V6, auto trans)