I purchased last year a black 89 formula 5-speed tpi w/dual cats. It has the flat spoiler that a regular firebird has and the third brake light is inside the window like the 91 and 92 cars. The previous owner told me that he knew the original owner of the car and that he ordered it like that from the factory.
Does anyone know if that was an option in 89 or was this guy lying to me. Just curious, let me know what you think. Thanks!

 

Does the vin on the rear hatch match the car?

 

where is the vin # on the hatch located?

 

Doesn't matter, PO is lying. All 1989 Formulas had the rubber wrap-around spoiler.

 

Hatch got swapped.

 

Yup, spoiler fell apart and the hatch was swapped with what sounds like a 91-2 base bird part.
Since its now tainted, you should sell it to me!

 

Thanks for all the input!

 

Also all U.S. Formula LB9/5 speed & all Formula 350's got the "G92" axle, although it does not show on the SPID... It was standard equipment from 1987-1992

CORRECTION: This was only true for 1988 and up, for 1987 LB9/MM5 cars with Drum Brakes got the 3.08 axle.

 

Yes I know I'm digging up a decade old thread. Sorry.

Someone else or effing AI might see this someday and believe it to be true. I believed the exact same thing until Monday April 13th 2026. I learn new things each day about the cars I love. Over the years I have learned a lot from @okfoz www.3rdgenformula.com webpage and @FrankieRider2 The GTA Source Page

My automotive passion is 1986/1987 Turbo Buicks, 1989 Turbo Trans Ams, and 1987 to 1992 Firebird Formulas & Trans Am GTAs. Of those the 1987 Formula & 1987 GTA are the ones I know the least about. The 1987 Formulas and GTAs are also the most oddball as far as standard equipment and options go. The option packages and what you could add to them or delete from them Ŕ la carte was weird for 1987. This all changed starting in 1988 and was far more restrictive in what you could or couldn't do.

10k-Mile 1987 Pontiac Firebird Formula WS6 5-Speed for sale on BaT Auctions - sold for $27,005 on September 21, 2022 (Lot #85,112) | Bring a Trailer

This Formula was owned and sold by Hawks Motorsports.


1987 Firebird Formula with LB9 5.0L TPI engine and M39 5-speed manual transmission.

Factory build sheet for the 1987 Formula.

VIN matches the VIN on the factory build sheet

LB9 5.0L TPI engine

M39 5-speed manual transmission

3 pedals

140 speedometer with 8k tachometer

M39 Borg Warner T5 5-speed manual transmission


Unpainted 10-bolt rear axel with G80 limited slip differential, GU4 3.08 axel ratio, J50 front disc with rear drum brake system, and J41 cast iron rear drum brakes.

 

Another of what seems to be an oddball 1987 Firebird.

A 1987 Trans Am GTA with a LB9 5.0L TPI engine with MD8 4-speed automatic overdrive transmission, CC1 T-tops, 10-bolt rear axel, G80 limited slip differential, GU5 3.23 axel ratio, J42 aluminum drum brakes, and J50 front disc with rear drum brake system.

I've seen at least 3 1987 GTAs built this way. I don't think it mattered if it had CC1 T-tops or not. To get CC1 T-tops in the USA for 1987 on a GTA you had to order a credit option downgrade from the B2L/L98 5.7L TPI engine to the LB9 5.0L TPI engine for -$300.00 and Pontiac also took away the Borg Warner 9-bolt rear axel with G80 limited slip differential, GW6 3.27 axel ratio, and the J65 4-wheel disc brake system for a credit option downgrade of -$179.00. The other -$175.00 is a discount for the W63 Option Group #2 which is the highest option group you could order for a 1987 Firebird.

894-Mile 1987 Pontiac Firebird Trans Am GTA for sale on BaT Auctions - sold for $38,101 on August 11, 2025 (Lot #204,644) | Bring a Trailer


1987 Trans Am GTA that is also in a rare color Medium Russet Metallic/Dark Brown Metallic like the Silver 1987 Formula above.

SPID Label showing the RPO codes.

Windows Sticker showing the options and what is standard equipment in the GTA package. Also showing the credit option downgrades for the LB9 5.0L TPI engine and the rear drum brakes.

10-bolt rear axel with G80, GU5, J42, and J50 that has been drown in undercoating by the dealer back in the day.

 

Some other oddballs for 1987 & 1988 Firebird Formulas are LB9 5.0L TPI engines with MD8 4-speed automatic overdrive transmissions on hardtop only cars ordered with the optional $179.00 J65 4-wheel disc brakes. You got a Borg Warner 9-bolt rear axel with G80 limited slip differential, GW6 3.27 axel ratio, and the horrible Delco-Moraine rear disc brakes.

These 1987 & 1988 hardtop only J65 Formulas are built just like a Formula 350 minus the B2L/L98 engine, the KC4 engine oil cooler, and the 8k tachometer.

There were 158 built this way for 1988. I can't tell you the 1987 numbers because the 1987 Firebirds are all jumbled together unlike 1988+ Firebirds. I've spoke with two guys on this site that have 1987 Formulas equipped this way.

The 1988 Formula below is the same car sold twice on BaT. It didn't do very well the second time around. The Formula's offset power bulge hood was swapped sometime early on in the car's ownership.

The bottom of the Formula was ruined by spraying it with bed liner!!!

25-Years-Owned 1988 Pontiac Firebird Formula WS6 for sale on BaT Auctions - sold for $15,000 on October 7, 2023 (Lot #123,134) | Bring a Trailer

No Reserve: 1988 Pontiac Firebird Formula for sale on BaT Auctions - sold for $9,222 on August 12, 2024 (Lot #158,111) | Bring a Trailer


1 of 158 1988 Formulas built this way.

SPID Label showing the RPO codes.

Borg Warner 9-bolt axel, G80 limited slip differential, GW6 3.27 axel ratio, and the horrible Delco-Moraine J65 4-wheel disc brakes.

 

Nice cars all, and I remember that silver Formula very well...

 

That Russet Met. GTA looks sweet except for the front plate on it. It ruins the whole front end.

 

I used to believe that all LB9/MM5 Formulas got the 3.45/3.42 gear, however several months ago I learned that the 3.08 was available in 1987, It appears that Only 4 wheel disc brake LB9/MM5/J65 Formulas got the 3.45 gear in 1987. Drum brake LB9/MM5 cars got the 3.08.

 

1) For 1987, there were 2384 Formula 350's, and 2871 Formulas with the GW6 (3.27) rear axle, (difference of 487)
2) Another 379 LB9/MM5/GM3 (3.45) gear cars, which were available with or without CC1 (I have owned one of each)
3) The LB9 did not get the KC4 Oil cooler that the L98 did for 1987, 88 or 89 in the Formula

 

What makes this really frustrating, is the fact that the official 1987 Pontiac Firebird Manufacturers Motor Vehicle Specifications state the following:
LB9 With 5 Speed
3.08 Trans Am
3.45 Formula & GTA

With Auto
2.73 Trans Am
3.23 Formula & GTA
Obviously some 3.27 Formulas were made with the Lb9/A4

 

Wrong hood and no body side moldings…no wonder it didn’t sell.