# 10 Bolt 8.5in. 3.08 HELP



## mtman (Feb 2, 2014)

Hi, My 74 came with 10 bolt 8.5in. 3.08 gears. Now sitting up on blocks I turn one wheel and the other wheel does nothing and finally starts to turn. So I thought it was trashed, so I pulled the cover off to see what I could see. Well the oil was a little dirty but not muddy and no chunks of metal. All the gears look OK, so turning the wheel and watching inside it seems to turn ok but still waiting for other wheel to catch up. the ring gears # 2 GM 3804028 13 40 11 73 the 11 is questionable. Any help with what's going on in there ? Thanks Mike


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## 05GTO (Oct 6, 2004)

mtman said:


> Hi, My 74 came with 10 bolt 8.5in. 3.08 gears. Now sitting up on blocks I turn one wheel and the other wheel does nothing and finally starts to turn. So I thought it was trashed, so I pulled the cover off to see what I could see. Well the oil was a little dirty but not muddy and no chunks of metal. All the gears look OK, so turning the wheel and watching inside it seems to turn ok but still waiting for other wheel to catch up. the ring gears # 2 GM 3804028 13 40 11 73 the 11 is questionable. Any help with what's going on in there ? Thanks Mike


I believe it indicates;

13 = pinion gears #
40 = ring gears #

40 divided by 13 = 3.07692303

11 = November
73 = 1973

Possible a build date,

But I could be wrong!


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## torrid red sap (Sep 27, 2014)

*what it means to me is that you have a open type rear diff. as oposed to a limited slip rear diff.3.08 gears were designed for hyway fuel economy, and not for quick accelaration, when one wheel is rotated by hand, the other wheel rotates in the oposite direction , as long as diff doesn't whine or clunk when driving all is normal. Hope that answers some of your questions.*


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## chuckha62 (Apr 5, 2010)

Sounds like it is working as intended for an open differential.


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## mtman (Feb 2, 2014)

Thanks Gang, Looks like a total rebuild. Just need to decide the TH400, or pickup a700R4 Need to start a new thread about trans. rear tire size. Thanks Mike


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