I just picked up a Formula 350 car and it has drum brakes... did'nt remember that being an option on 350 cars.

 

My 91 Formula 305 TPI 5 Speed has Rear Drum... though it also had the G92 dual cats....

Raf

 

I've read that early in the 91 model year run GM had an issue with rear disks, can't remember what it was right now, they substituted rear disks with aluminum drums and offered a credit on cars ordered with a rear disk package.

I looked into this when I seen my TA has the R6P RPO which includes the J65 rear disk but also had the J42 aluminum rear drum RPO

 

Mine was made in 5/91 so it is a model made towards the end of the run. I've heard they only did this on the 91 models, not sure if it's true or not and not sure why they would do this either.

 

There was a shortage of the Disk brakes in 1991 for a period of time, not sure if it was from a Union strike or if there was some other issue... nonetheless some 1991 cars got Aluminum drums instead of the mandatory Disk brakes on the 350 cars...

Effective July 30, 1990 Cars that were previously mandated to have disk brakes came with Aluminum drums. The only exception to this was the G92/1LE cars. Prior to this Discs were Optional on the Trans Am with the LB9/M5 and Required on the Formula and GTA with the LB9/M5/ and Required on all the L98/A4 cars. They no longer accepted orders as of July 16, 1990.

they were replaced with the J41/J42 rear Drums,

Effective May 28, 1991 4 Wheel disc Brakes returned, Orders could be made as early as May 7, 1991.'

So from July 30, 1990 thru May 28 1991 there were no Disc brake cars EXCEPT the 1LE cars... Might include the B4C cars tho, not sure.

John

 

Ahhhh.... that explains it perfectly!!! Thanks for the quite well informed answer.

 

A while back I had found a 91 GTA 350 TPI Car in a local junkyard and it too had rear drum brakes.I thought that was kinda strange

 

methinks some previous owner swapped something. Either not a legit formula, or it was built with the LO3, or the rear axle was swapped. If GM built it this way, I'd be surprised.

 

My 1991 GTA 5.7L Auto had aluminums drums on it from the factory! ! !

 

Read my previous post, it explains the whole thing...

John

 

That's what I remember the dealer told me back then also.

 

The cancellation, with exceptions



The reindtroduction:


John

 

Yes they came with rear aluminum drums with a small discount on the the G92 performance axle ratio package...I bought a new formula 5.7L in December 1990 after having a 230hp 5.0 5 spd on order for months and being delayed due to parts shortages and slow sales extended plant shutdown from before Thanksgiving to after Christmas...91 was a bad year for GM F car production... very low numbers