1967 caddy rear gear ratio

[29tons]

I have a 67 caddy rear I see no tags on the outside the only thing i see is a casting number on the pumpkin which is 1482958pd464. its a posi and has the perfect measurements for a truck that I am building.Do those numbers mean anything as far as ratio or do I have to pull the pumpkin out?  If so how do I tell what the ratio is

[C Carl]

Well , look , you have the whole 3rd member out , so why don't you and a friend just count it ? As you make one entire revolution of the rear axles , the input flange will have made just under , or just over three revolutions. That is close enough for your purposes. You could then look up the exact ratio (3.07 for example , or 2.something) if you are curious. Make sense ? Speaking of curiousity , please tell us about your truck build. Good luck with it. Most of us old guys wish we still had your energy. Use it well while you have it !  - Carl

[joe_padavano]

As described, it really is just that simple. Count the turns of the pinion flange to get one then of the axle flange. This assumes the posi is working and both wheels are turning the same amount. 

 

Since it can sometimes be tough to discern 3.23 from 3.42 (for example), I like to go ten turns on the axle flange. It's pretty easy to tell the difference between 32.3 and 34.2 turns of the pinion. 

[intimeold]

Rear Axle: 
Hypoid. Differential housing offset to provide straight-line drive. Ratio is 2.94 with a 3.21 axle available (3.21 only on Eldorado). The 3.21 axle is standard on all air-conditioned models and the Seventy-Five models. Available (except Eldorado) is the controlled differential which directs power to the rear wheel having better traction.

 

I just googled 1967 Cadillac technical specifications and got this.

 

So it looks like you have 2 choices; if it is stock; probably is.  Not too many 1967 Caddys were drag-racers.

 

So do the math or take it apart and count teeth.

 

I didn't change any wording in that spec; but that last sentence seems odd. I copied and pasted it. (Yea, I saw it on the internet) OH MY

 

intimeold

Edited August 31, 2016 by intimeold (see edit history)

[mike6024]

If it was me, instead of turn the axle one time, and count the pinion 2.9 or 3.2; I'd rather turn the axle 10 times and count the pinion 29 or 32.

[C Carl]

Since intimeold has given us the only two possibilities , you only will have to turn the axles one complete turn. That pinion flange will turn just shy of 3 times , or almost 3 1/4 times. The ten turn trick certainly has higher precision , but you don't need it in this case. Usually old age comes with diminished ability to concentrate. I am in that group. I probably would have trouble counting all those extra turns. Use it or .................. - Carl

[29tons]

thanks for the info 3.21 axle with the tall tires may not work to well. its a 1947 chevy cab over with a 1956 chevy six 235 someone started this project and spent a lot on the engine even ran it on the floor for an hour hooked to a radiator put it in the truck drove it for a couple hours and valve stuck and hit the piston. so the engine has to come apart. The rear axle is a 2 speed with low gear at 8.10 and high at 6.13 so since the truck is never going to haul heavy loads I would like to find a 3.73 Posi . I Found a place that makes wheel addaptors very reasonable. They said they can put almost any rim on any axle.oh Im 53 and I know what you mean by no energy when I was 18 I could not wait to get home and work on an old car now I can barely get to the garage a couple hours on the weekend