Rearend Question

I need to get some opinions on something. I broke my rearend last weekend at the blue suede cruise in Norwalk, took out the spider gears. It's a '59 chevy stock rearend. I got another complete center section from a super nice older guy who gave me a smokin deal. Here's my dilema. The broken diff has a 9 tooth pinion and 32 tooth ring gear which works out to 3.555556 and the one I bought has a 11 tooth pinion and a 39 tooth ring gear which equals 3.5454545. Is there a strength issue here? I didn't realize that GM used different tooth combos for the same ratio. The 9/32 has a '59 date code and the 11/39 a '56. Should I just put the '56 unit in as is or should I take the spiders from it and repair the '59 unit?

Thanks, Fred

 

The 59 chevy parts book I have shows the 32/9 used for all 55-56 pass cars w/PG, but there's a note that early design was 39/11. Also there is a different part number for the 3.55 gears used from 55-56 and from 58-59. and 57 is different yet. And there are a bunch of different part numbers for the differential case.

But the spider gears are the same number for all of them from 46-59 without posi...

 

Which ever has the thicker ring gear is stronger, as a rule of thumb. Your best bet is to keep the set matched. Not only will you avoid any surprises, but the wear on the parts has mated them. Swapping now will lead to short lived parts.