I was just curious... Does anyone have a 91 or 92 Convertible with rear disc brakes???

According to one source they did not exist, just testing to see if anyone has a Factory J65 car.

John

 

Not here, and one just like mine that just showed up on Ebay did not either. I usually check the verts on ebay and can't say I've ever seen one.

Kevin D.

 

Mine rocked drums factory.

 

I just picked up a 92 convertible how can i tell if its a 305 vs a 350? Its automatic z28 i assumed all z28 came with a 350 is that correct?

Also drum brakes.

 

After some searching and From what I can tell, 4 wheel discs were NA on the factory convertible in 91 & 92...

John

 

Both my 91 and 92 have drums. Yet they went out of their way use an aluminum driveshaft.
Was there some weight penalty with the disc's?

 

I am honestly not sure if one weighs more than the other... I would think that drums were heavier, but I have never weighed the assembly to find out. I do know that the later 89-92 rear discs were heavier because there 1.25" dia larger, they would almost have to be. The Calipers are lighter on the 89-92 however, but I am not sure about the total offset.

Interestingly from 82-88 cars with 4 wheel disc brakes and cars with rear drums used a different proportioning valve. When they went to the larger rear brakes in 1989, mid year, I want to think that they went to the same prop valve, and the sytems were more identical than ever.

I know that drum brakes are stronger stopping, for one stop or two stops, beyond that they swell and they have "Fade" The aluminum drums cool better and do not have the severity of fade. Its actually a misconception that discs are better because they are stronger, discs are used for performance because they do not fade, not because they are stronger. The convertible was probably not intended to be a performance orientated car destined for the track, so the addition of disc brakes may have been more than what GM wanted to deal with. Honestly I am not sure if they would have to test cars with and without disc brakes for the EPA...

Looking at the Dealer Order Worksheets for Convertibles there is nothing there to indicate that the J65 disc brakes were even an option...

More or less you got to chose the following:
Engine, LH0, L03 or LB9 (The LB9 required the G80)
The Tire size, (in this was included a WS6 option)
The color of the car & Color of interior.
Option packages 1SA 1SB & 1SC

Your other items, like Power Antenna, License plate bracket, Claif Emissions, Radio and choice of Transmission.

There is nothing it indicate that the convertibles had an optional rear disc brakes... At least on Pontiac side...

John

Interestingly the only way to get AC delete was to order a V6 car, stripped to nothing.

 

According to Compnine's database, none of the 1992 T/A (663) had the rear disc brakes. I checked into this myself as mine has rear drums. Even those that had WS6 (which I know doesn't mean rear disc brakes, but does make it more likely due to added equipment) didn't have rear disc brakes either. I'm 99.9% sure I see some documentation that said J65 was N/A on the Convertible, which was the final word for me, but I cannot locate it at this moment.

 

I also checked compnine, but I also knew that they were about 90% complete, but I had to check anyways to see if compnine may have been in err

Thanks JT...

Also did you happen to get my email with the information you were seeking?

John

 

John, while they are missing a certain % as you said, notice they show 663 Trans Ams Convertibles for 1992. That is the same figure we show and has been floated around.

So while they may be a % short on overall 1992 production, my suspicion is the figures are accurate on the 1992 T/A Convertible side (as much as possible) since they have all 663 1992 Trans Am Convertibles in their database. I would suspect the % missing would only be applicable to the hardtops/T-tops.

 

Actually I did notice that 662 number. I checked the 1991 numbers and that appears off...

I want to think that the 662 number was not always there, so its a newer revelation. Ultimately I hope that they find all of the information, for all years... that would be awesome.

John

 

Hey John, you mean the 663 number on our site or on Compnine site? If our site, it has been there for years. On Compnine site, it has been there since roughly the site was first posted about here on ThirdGen as I recall checking on my 1992 T/A Convertible. It would be great if more VINs/RPOs were being discovered for the ThirdGen, but I haven't seen any clear indication of such - especially for the earlier years.

However, I never checked the 1991 T/A Convertible figures so I really don't know about that one. I merely checked the 1992 figures being an owner of a 1992 T/A Convertible myself and having the exact same question you did about J65 and if it came on any 1992 T/A Convertible or not.

I'm still sure I seen "NA", somewhere, on J65 and the 1992 T/A Convertible but I've not looked too hard to relocate that info.

 

My '91 has rear drums and all the literature I have says only drums were offered with the 'verts. Never ran across one with stock discs.

As for '91 Trans Am Convertible production numbers, Pontiac, by letter, told me that there were 555 produced. However, another letter from Jim M. at PHS said the total was 637. He said that the 555 number was likely the US figure and did not include Canadian vehicles.

 

Drums here too...can't say I have seen one with disc's...although I am consdering adding them to mine.

From what I know about convertibles, I agree with the others that this was not an option in 91-92. Other years may have them, since those cars were not VIN'd by GM as verts but rather HT cars...so more options may have been possible.

 

ive seen them but to be honest I never looked at rpo tags or even asked if they added them.. I think its looking like they were added by the owners later in life

 

I had drums too. Upgraded to Ed's LS1 fronts and later swapped out the rear for a better gear and PBR's.

Best change I ever made.

 

This makes no sense to me. If GM was pulling cars off the line and sending to ASC, WHY would they care if it had the G80 (Limited slip) & J65 (4 whl disc) packages? There were no "written" restrictions for the combo - except they had to go together. I know this because when I ordered my 86 IROC, I wanted G80 and they told me I had to have J65 with it. To my knowledge, the vert only had a restriction on the 5.7L. I have some sources to run this down.

 

I checked with a dealer friend who shows no restrictions in 86/87 on J65, other than coupled with G80. I also know of two third gen low-mileage verts (one in my family) that had rear disc brakes. That's not to say there might have been some in later years for some other reason though...

 

The issue is, this topic is about 91-92 Trans Ams Convertibles, which is a bit different of an animal. Camaros and Firebirds were not always treated equally, and things certainly changed from mid 80s to late 90s. In addition, the early Trans Am Convertibles were "unofficial" through dealerships and could be ordered nearly any combination because they all left as either hardtops or t-tops from the factory.

When the 1991/1992 Trans Am Convertible was official from Pontiac, and not through dealerships, there certainly was restrictions. In fact, there were some 1989 Trans Am/GTA/Formula Convertibles with the 350. This was not an option, at all, in 1991/1992 Trans Am Convertibles. Nor was a GTA Convertible an option in 1991/1992.

I'd invite anyone to find a 1991-1992 Trans Am Convertible with J65. According to Compnine's database, which shows all 663 1992 Trans AM Convertibles, none of them had the J65 option. If J65 were an option, chances are someone would have ordered it.

 

JT,
I would concur that indeed there would have been at least one if it was available, I would think it would have been more popular than zero.

Honestly, I think the thread is dead, its been determined that there were zero J65 convertible Camaros or firebirds for 1991 or 1992... Dare I add 1990. Possibly 1989, jury still out on that one. At least no 1989 Canadian Convertibles with J65...

John

 

Mine is a WS6 car and it had factory drum brakes.

........of course now it's a 1LE 4-wheel disc car :O)

 

Let me get this straight, RPO G80 on my car is limited slip with drums. Are all TA verts equipped with this rear? What gear ratios are these rears?

 

If we're speaking of 1991-1992 T/A Convertibles, none of them had J65 (Rear Disc). As far as gears, the LB9/5-speed had 3.08 rear rears while the LB9/Auto had 2.73. All of these had G80 (positraction). The L03 TBI engine did not have G80.