12 bolt rear axles
 

Well guys I ran into a new one for me...

I have a '73 (per the title, '74 per the VIN) Suburban that I picked up and did some investigation on the rear axle for servicing it. It turns out it is a 3.07 gear with a factory LSD carrier and the pinion yoke takes a 1330 series U-Joint. The ring gear is stamped 14 43, which works out to a 3.071428571 ratio.

I also have another 12 bolt from a square body (not 100% sure what it originally was in before I got it). It is has 3.07 gears and an open carrier. The pinion yoke on this one takes a 1310 series U-Joint. The ring gear is stamped 15 46, which works out to a 3.066666667 ratio.

All the other 12 bolts that I have and have had in the past have the same pinion yoke size that uses the 1310 u-joint.

Has anyone else seen 12 bolts with the same ratio, but different tooth counts and a different pinion yoke?

Would GM make multiple sets of gears that work out to the same ratio for the same type of axle? What would be the reason to do so?

Re: 12 bolt rear axles
 

Probably the year manufactured has something to do with it. The early 74 may have had the R&P from a earlier run, and there could lie the discrepancy.

Re: 12 bolt rear axles
 

Get a 14 bolt and pat yourself on the back.

Re: 12 bolt rear axles
 

Why? That is not really an option since it is WAY overkill for the intended use.

Also, it would cost me $$ to get one when I already have a good useable rear axle.

Re: 12 bolt rear axles
 

I am going to dig into the year manufactured also, but so far from what I have seen, the pinion yoke difference may be do to the fact that the original engine in the suburban was a 454. I have read that those had the 1330 style u-joints...

Re: 12 bolt rear axles
 

Curious to see what you find out. I have a 1979 Suburban with a 454/TH400/3.73 open in my yard.