The doors will interchange, but they are very difficult to access internally to retrofit with electrics, windows, and locks etc., so get a door that is already loaded with what you need.
A problem with '85-and-later"vented" Trans Am/GTA hoods is that they kink in the middle because the holes for the long vents weaken them. The '82-'84 Trans Am and '87-and-up Formula "power bulge" hood is stronger and fits perfectly on any '82-'92 Bird or T/A.
"Aero Wing" rear spoilers are not only prone to cracking and chunking if exposed to the elements, they are also very heavy. Replacing one with an earlier solid pedestal-style spoiler will save you about 40 pounds, and it will hold up much better than the later foam-over-steel Aero Wing. An aftermarket fiberglass "Aero Wing" is available, which saves weight and is more durable, but it's not cheap.
Another source of goodies for the Third-Gen cars is the recent appearance in the yards of the Fourth-Gens. All rear suspension components will interchange, though the rear end is wider and will require Fourth-Gen offset wheels. The front seats bolt in, and the rear brakes, by employing the correct Third-Gen mounting brackets and parking brake cables, can be swapped in as well.
Up front, the suspension is completely different, as is the bodywork. Installing a Fourth-Gen engine (LT1 or LS1) will require significant modifications but makes for a very nimble, light, and easy to service Third-Gen.
Which Rear Gear Do You Have?
To determine the gear ratio in your current rear end if your tag is missing, get both rear wheels off the ground and put the car in neutral. Turning one wheel by hand, look at the opposite side to see if the wheel is turning in the same direction, which is limited-slip. Look at the opposite wheel and if it's not turning at all, it's open differential. If you have an open differential, you'll need to put one tire on the pavement or have someone/something hold it stationary. For a limited-slip differential, you'll need both tires off the ground.
Mark the tire you'll be turning and the driveshaft (or yoke) to keep track of the rotations. As you turn the wheel once, count the revolutions of the driveshaft, and at TDC. Again with your turning wheel, estimate the percentage of the last rotation that the driveshaft has made. If your driveshaft has made three full rotations and has turned about 20 percent of another rotation, your gear ratio is in the 3.20:1 range. Looking at the chart, we see that our example of an '88 GTA 9-bolt was available with a 3.27:1 performance gear ratio with automatic transmission, an excellent upgrade for a 2.73:1 rear end. T.A.
|Third-Gen Rear Gear Application Chart|
|Years||Model||Trans||Engine||Displ.||Induction||Manual||Man Perf||Auto ||Auto Perf|
|code/type||Std||Option (G92)||Std||Option (G92)|
|'82-'83||TransAm,||M4,||LU5 V-8||5.0L (305)||CrossFire||3.23||N/A||2.93||3.23|
|'82 Only||Firebird,||M4, A3||LG4 V-8||5.0L (305)||4 bbl||2.73||N/A||2.73||N/A|
|Trans Am, Z28,|
|'83-'85||Firebird,||M5, A4||LG4 V-8||5.0L (305)||4 bbl||3.23||3.73||3.08||3.23|
|Trans Am, Z28,|
|'86-'87||Firebird,||M5, A4||LG4 V-8||5.0L (305)||4 bbl||3.23||3.73||2.73||N/A|
|Trans Am, Z28,|
|'83-'85||Trans Am,||M5||L69 V-8||5.0L (305)||4 bbl H.O.||3.73||N/A||3.42||3.73|
|'85 Only||Trans Am,||A4||LB9 V-8||5.0L (305)||TPI||N/A||N/A||3.23||3.42|
|'86-'92||GTA, Trans||A4/M5||LB9 V-8||5.0L (305)||TPI||3.08||3.45*/-90||2.73||3.42/-88|
|'88-'92||Trans Am,||M5, A4||LO3 V-8||5.0L (305)||TBI||3.08||N/A||2.73||N/A|
| ||Formula,|| |
| ||IROC-Z|| |
|'87-'92||GTA, Trans||A4||L98 V-8||5.7L (350)||TPI||N/A||N/A||3.27*/87||3.27*/88,89|
| ||IROC-Z|| || || || || || || || |
|’89 Only||Turbo||A4||LC2 Turbo||3.8L (231)||SFI||N/A||N/A||3.27*||N/A|
|Trans Am (TTA)||V-6||Turbo|
|*Borg-Warner “Australian 9-bolt” rear axle|