Ram Air GTOs vs Firebirds
 

Why would Pontiac made 4.33s the only available gear from the factory for GTOs, while Firebirds got 3.90s?

It wasn't the only gear available, but was the standard gear in 67 & 68 and optional in 69-70.

Perhaps I should clarify.

In 1967-68, Ram Air GTOs came standard with 4.33s with no higher gear from the factory.

But equivalent Firebird 400s came standard with 3.90s.

Why the difference?

I'll take a stab at it. The factory was afraid that the Firebird might be faster than the GTO? :)

My guess would be it just had to do with the weight of the car. Someone at Pontiac had in mind the way a Ram Air car should launch, and it took a 4.33 to get a GTO to "meet the target", while the Firebird could perform similarly with a 3.90.

If that was true, why did they made the gearing identical for 1969-70 RAIV?

My thought was mainly the smaller tire on the 67/68 FB vs. the GTO. The throttle limiting tab may have also played a part in it.

Starting with RAIIs, the tab was gone so it did not matter in 69.

i know of a documented 67 Ram I convert...i saw the paper work..it was 4.33 geared....i didnt know that wasnt available

Mark, it was the only one available - that's what I'm saying. Strange they didn't offer 3.90s like on the Firebird.

My guess is the weight difference between the cars. As Keith mentioned above, an engineer probably calculated what the rpm these vehicles would be going through the traps. The 4.33 gear worked for the 67-68 GTO, and the 1967-1968 Firebird 400 was about 150-200 lbs lighter than than the Goat, so 3.90 gears were ideal for the Bird. By 1969, the Firebird gained some weight, so the gear ratios evened out.

oh i see..i thought ya ment 3.90s only..brain fart

Do you have documentation that "no higher gear" was available? On what are you basing this statement?

It's my understand that although the 4:33 & 3:90 were standard you could order a higher (numerically lower such as 3:55) gear.

^^This!^^
Ok... I'm just guessing here also...
The GTO was Pontiac's "Corvette" - their marquee performance car. It was probably never publicly stated, but I bet behind the corporate walls there was an unwritten decree that no Firebird would be faster than the top GTO. I guess by 1970 the GTO had lost it's "mystique" and the Trans Am became the alpha dog.

This is same conundrum Porsche is having with the 911 and the Cayman... Porsche will never allow the Cayman to have the same horsepower as the 911 knowing that the less expensive Cayman would run rings around the "legendary" 911.

Well beyond the order sheet -power to weight transfer A bodys hook up better than F bodys im sure GM knew this id say a bird with 4.33's would just smoulder the tires for a while
but ill add this-- whats the steepest rear that a camaro guy could check off ? i know 4.11 for sure but beyond ?

It's something that I noticed years ago.

http://www.oldcarbrochures.com/stati...rebird-12.html

http://www.oldcarbrochures.com/stati...ige-54-55.html

Boss is right coulda got what ever you wanted if you so inclined to special order

That's interesting considering the links I provided show the opposite to be the case.

I wouldn't call that conclusive proof counselor.

Show me a 3.90 RA GTO from 1967-68.

i know my eyes arnt the best but i did read at the bottom different ratios could be dealer- installed- so my best guess is the came from the factory ( RA gto's) with 4.33's if you wanted something different it would have been dealer installed my guess is that in those days you didnt have the time- patience or the $ or the knowlage to ask the dealer to change the rear end -im sure a small handfull did but not too many