1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Are all 12a LSDs the same?

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Old Dec 15, 2006 | 04:01 PM
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Are all 12a LSDs the same?

Just like the title said, I had to replace my axle on my 82 gsl. I just picked up an axle from the 84, I'd like to know if the LSDs are the same so I can rebuilt one while I drive around on the other?

Thanks,

Alvin
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Old Dec 15, 2006 | 04:04 PM
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Are you refeering to the diff or the axles because the axles are different in 84-85 as far as the bearing size.

Diffs changed the size of the flange in mid 83-85. So you need to change the driveshaft.
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Old Dec 15, 2006 | 04:07 PM
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i think the actual lsd unit is the same.
they switch from 24 to 27 spline axles though.
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Old Dec 15, 2006 | 06:27 PM
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Yup, I mean the LSD unit, what I want to know is if I rebuilt my LSD from my 82, will I be able to bolt it into the 84 rear end and axle.

Alvin
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Old Dec 15, 2006 | 08:13 PM
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actually part of the lsd unit would be threaded for the splined axle so i dont think it would work. the clutch disc are the same though i bet.
sorry im not more help but i have neven taken a lsd unit out before.
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Old Dec 15, 2006 | 08:20 PM
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I am going to have to say no if the splines are different. And you cannot use 84-85 axles in the 79-83 housings.
Someone please correct me if this is incorrect.
I have only swapped complete rear ends and replaced diffs for diffs or upgraded Se units into 84-85 models.
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Old Dec 15, 2006 | 09:00 PM
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Looking through my 1980 Differential Overhaul manual, along with the 85 FSM, it is the side gears that the axle splines mate to. If the side gears with different spline counts are interchangeable between the 2, it may work. It will require tearing down and rebuilding the diff to change the gears.

Simple answer to your question is no. You would need both units torn down to swap side gears, and there is no guarantee if they are even intechageble. Not only the side gears, but the diff units themselves.
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