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Old 09-25-2010, 06:00 AM
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78 series rear end

Will a 78 series rear end from a f body gm fit a g body gm?

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Old 09-25-2010, 06:32 AM
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Quote:
Originally Posted by redsag 78
Will a 78 series rear end from a f body gm fit a g body gm?
Depends on the year, but there is no direct swap, some parts will swap, or nothing will swap.

'71-81 F-body rear is 8.5" ring gear and is leaf spring, all 78-newer A and G-body's are coil spring, so the housing is not a swap. Some G-bodys have an 8.5" rear(the Buick Grand National and T-type V6 turbo cars, and some of the Olds 442 and Hurst Olds) so you could swap gears, and posi units, but that is it. The rest of the G-body's got the pee wee 7.5" rear, nothing from the 1978 F-body rear will swap.
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Old 09-25-2010, 06:41 AM
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The m78 is from a 87 iroc. It is also known as Borg Warner 9 bolt. What is the difference in width between the f body and g body rear end?
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Old 09-25-2010, 08:53 AM
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The F body rera end is quite a bit wider than the G body rear end. The G body is 58 inches wide and I think the F body is around 63 inches. The suspension is completely different. This would require a lot of fabrication to make it work.
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Old 09-25-2010, 01:44 PM
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Thank you. Will the 7.62 gears replace the 7.5 gears. Will the 28 spline GN axle work in the m78, which is also a 28 spline. I don't think the m78 uses c clips, does the GN.
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Old 09-25-2010, 02:10 PM
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Quote:
Originally Posted by redsag 78
Thank you.
Will the 7.62 gears replace the 7.5 gears?.
Will the 28 spline GN axle work in the m78, which is also a 28 spline?
I don't think the m78 uses c clips, does the GN?.
I don't think anything from the m78 will work in a 7.5" rear.
8.5" GN axles will work in a 7.5" G-body rear if the 7.5" Diff uses 28Spl.
GN axles are retained by C-clips.
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Old 09-25-2010, 02:23 PM
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Thank you, this rear end was a possible way to improve the gear ratio for my 200r4.Well back to reality, thanks again.
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Old 09-25-2010, 04:44 PM
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If your car has the 7.5 10 bolt then you can get gears from a S truck. Many of them have 3.42, 3.73 and even 4.10 gears. If you have a 3.08 to 2.41 gear then you will also need the 3 series differential to go with these gears. If you have the 8.5 GN rear end then you can get gears from the 1/2 to truck. Many of them have these same gear ratios.
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Old 09-25-2010, 05:27 PM
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I found out that the posi from the m78 would fit the g body. Do you know what carrier the m78 uses?
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Old 09-25-2010, 07:50 PM
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This is a Borg Warner rear end made in Australia. No parts in it will interchange with the GM 7.5 or 8.5 10 bolt rear end. The Borg Warner rear end uses a 4 pinion cone type differential and there is NO way to use it with c clip axles. It will not fit the GM 10 bolt rear end.
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