Drive trains and popular options: In 1970, the Trans Am engine was a 400 cubic inch V8 available as a Ram Air III with Ram Air IV optional. For 1971, the Ram Air engines disappeared and were replaced with a 455 High Output (HO) version. The Trans Am engine for 1972 was also a 455 HO. They were available with four speed or automatic transmissions. New for 1973 was a 455 Super Duty engine which included round port heads, aluminum manifold and special exhaust manifolds, high lift camshaft and four bolt main blocks with webbing. The SD455 was optional and the base 455 was standard. The SD455 option was available in 1974 in limited quantities. The other engines available were the base 455 and the 400, which returned as an option for the first time since 1970.
For 1975 the only engines available were the 400 and 455. The 455 was extremely limited as the option was dropped as engineering changes to the transmission cross member and new catalytic converters were being implemented. In 1976, the 455 returned for the last time as the premier option while the 400 was the base mill. For 1977, engine choices ranged from a new W72 high performance 400, a base 400 and an Oldsmobile 403 V8 available in California only that year. From 1978 to 1979 only two engines were available nationwide; the 400 Pontiac and the Oldsmobile 403. In 1980 the engines were limited to a 4.9 liter four barrel Pontiac and a turbocharged 4.9 option. In 1981, the Pontiac V8 ended production, necessitating a switch to the Chevrolet 305 V8 about half way through the year.
The 455 is the most favored engine followed by the W72 400.
By March 1981, only the Chevrolet 305 V8 was available.
Popular options include power windows, air conditioning, tinted glass, honeycomb wheels on '71-76 cars, forged aluminum wheels on '77-'81 cars and hatch roof panels from '77-'81. Technically the hatch roof panels were available in 1976 but only on the 50th Anniversary Trans Am. The favored engines in order of desirability are the 455 HO, the standard 455, the W72 Trans Am 400 and a tie between the Oldsmobile 403 and the base 400. The last performance engine was the turbo 4.9 V8 from 1980-81
What to Look For: When buying a Trans Am, ninety percent of your time is spent looking over the unibody. These cars are major rust buckets. Here is a list of the weak areas you have to check with every year Trans Am. The rear axle kick up and rear frame rails, the rocker panels including the door sills, trunk lid and floor, lower quarter panels, rear fender spats, front fender spats, tops of front fenders. The hood hinge, supporting sheet metal and cowl area joining the dash to windshield are notorious rust areas.
It's common to replace lower rear fenders due to rust. Patch repairs panels have been made for years, but you still have to find donor pieces if you're replacing an entire rear quarter panel. Trunk lids often rust from the inside out and what is visible is just a small portion of the cancer. You're wise to replace the entire lid.
Rear fender patch repairs are very common due to trapped dirt under the fender spats.
The hood hinge, supporting sheet metal and cowl area joining the dash to windshield are notorious rust areas .In addition, the windshield pillars at the base of the metal dash are notorious for rusting. Many amateur repairs with filler have been done which only makes it worse as metal filler holds moisture. If the car has holes in the corner of the dash larger than most coins, I would pass on it. On a car with hatch panels, this can be a real problem. Shown is a picture of the entire area to be checked thoroughly especially on a T roof car.
Condensation cycles can rust panels from inside out. It's cheaper to replace with new metal than repair this trunk lid.
Use a business card to check for rust between the fender spats and sheet metal. If you pull it out and rust stains or debris shows up, you could have repair work. Remove the sill plates and check the rocker panels. Usually, you'll find rust at the bottom where the rear fender meets the sill. Likewise, rust out occurs where the sill meets the front fender above the fender bolts. The engine sub frame is a bit weak on the pre 1976 models, so rust out can be a problem. The '77 and later sub frames are better but all of them suffer from rusted cage nuts and bolts, making bushing replacement a big job in a complete restoration.
The entire hood hinge and metal cowl area into the windshield pillars are notorious for rust. Check it carefully on hatch roof cars.