Posi?? or just broken diff?

I recently broke a spider gear in my 12 bolt under my 65' c10 longbed, and it messed up the carrier, and chewed up some gear teeth. Also in the process of things breaking i guess the axle retainers popped off, and well you can guess what happened... So anyway, I just came across a 68 c10 rear end with 3.73 gears, but when i checked for posi, with both wheels off the ground i spun one and the opposite one spun in the same direction, however when i turned the yoke both wheels spun in opposite directions??! I am not that familiar with what a posi will do when its broken but can anyone make sense of this? Any help will be greatly appreciated, thanks.

 

Have someone hold one and you turn the other. A open diff will let just one turn. I'm suspecting 50 year old grease is causing what you describe.

 

I agree

 

Why not get rid of the problematic and lowly rated 12 bolt and put a 9" in there (like millions before you have already done)?



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Maybe because they don't bolt right in.

I agree, it's probably not a posi -

 

That doesn't slow most people down.



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I almost went with a 9 inch but its tough to find one that fits my width, also I have 6 lug so it would be more work then i need for just a daily driver. Aside from that am i asking for trouble putting old used gears in my truck?

 

No way turning the yoke can turn the wheels opposite directions. One can turn while the other doesn't, or they both turn the same way. Or if something is busted, neither turns either way.
Holding the yoke and turning one wheel will make the other one turn backwards, unless its a posi. Then nothing should move.

 

Its an open diffy. If you turn one tire in one direction the other will turn in the opposite direction and the yoke will not turn. If you turn one sometimes the yoke will turn and not the other side. Also, you can sometimes turn the yoke and both wheels WILL turn in the same direction due to dry greas eon teh spiders, or crud in the drums, or something like that. If you turn one tire and the other goes in the opposite direction it IS an open carrier.

 

BTW a GM 12 bolt is a tough rear end, equally as strong as a 9". A 9" is more popular because of the removable carrier, and a 12 bolt is tougher to set up and change gears in. There is also more beef up stuff available for a 9", so it can be made even tougher yet (at a pretty high cost though), but in stock configuration there is no real strength difference between the two.