[cowdoc]

I have a 67 firebird convert. It is an original v8 car with an open rear end. When I spin the rt tire 1 revolution I get under 2 revolutions of the driveshaft. What do you think my gear is and did this car probably come with an 8.2 rear end?

[cowdoc]

I have a 67 firebird convert. It is an original v8 car with an open rear end. When I spin the rt tire 1 revolution I get under 2 revolutions of the driveshaft. What do you think my gear is and did this car probably come with an 8.2 rear end?

[cowdoc]

forgot to mention that it was a powerglide car also.

[67ConvFB]

Your car originally came with a 8.2, but after all these years, that doesn' t mean that is what is still in there. As to your gear ratio, only raise one tire off the ground with an open rear, or just pop the cover and know for sure.

[einstein]

Before you take off the cover, check for the two-letter code on the left axle tube. Usually a couple inches from the center section, and typically hidden under the steel brake tubing near the welded clip. Wire-brush that area and report the codes here. We'll ID it.

[bird412]

On an open rear end, only raise one wheel, but you have to spin it two revolutions while counting the driveshaft revolutions.This will give you the approximate ratio.With a posi, raise both wheels and spin them once.Remember to put the tranny in neutral and block the front wheels.

[Steve Shively]

Wasn't the axle code in '67 on the right axle tube or am I wrong?

Steve

[cowdoc]

I had to pull the axles to change the bearings so I took the diff cover off to change the lube. Counted the teeth on the ring and pinion and figured out I have a 2.92 rear. No wonder the thing is a pooch out of the hole. What are my options for lower gears?

[Charlie Jones]

Cowdoc,
The lowest ratio you can go to by just changing the ring and pinion is 3.23. If you change the differential case ( the part that the ring gear bolts to, NOT the axle housing) then you can install any ratio from 2.56 to 4.33.
The following information was gleaned from the Pontiac Master Parts Catalog(1972)
There were three differential cases used on 1966 to 70 "A"(Tempest,LeMans,and GTO), "F"(Firebird), and "G" (Grand Prix) bodies.
# 9782417 was used with 2.56(41-16)and 2.78(39-14) ratios.
#9782418 was used with 2.93(41-14),3.08(40-13),and 3.23(42-13) ratios.
#9782419 was used with 3.36 (37-11),3.55(39-11),3.90(39-10),4.11(37-9), and 4.33(39-9) ratios.
Posi axles also followed the same pattern with three different diff. cases.
From what I can see, any complete set of internals from any of the above mentioned cars should interchange. If anyone else feels I'm wrong please feel free to correct me.