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Thread: AXLE LENGTH

  1. #1
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    AXLE LENGTH

    have factory rear in my `57, with a posi. are the axle lengths the same for a non-posi rear? going on a long trip, would like to change center sections for the trip. thanx!

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    Registered Member BamaNomad's Avatar
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    From what I've read, that depends on factors you haven't provided in your post. Depends upon whether your rear end/differential was updated from a non-posi to a posi in the past. When doing that, it is generally required to cut ~ 1/4" off the ends of the axles, so... Are axles in your rear shortened for that or not? Is your differential an original posi from Chevrolet? or not?

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    factory posi. are they cut? if you need to have them cut for a posi, then i guess they were. do non-psi axles fit in a posi? if not, i guess they were cut. one is shorter than the other.

  4. #4
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    If your car came with a posi, the axles are 1/8" shorter than with an open differential. The driver side axle is shorter than the passenger side.

    With axles correct for a posi, you can put either a posi or non-posi center section in the car and use the same axles.

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    thanx, that`s what i wanted to know.,,,,,,ok,, rick L. from the other forum?

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    Registered Member Dragsix's Avatar
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    Dave, if the rear is an original 57 posi assembly, and by that I mean that particular differential housing, center section and axles, are original posi pieces, then the axles that were installed at the factory were shortened a bit (1/16-1/8) so that the ends of the axles would not bump the posi cross shafts in the dana 44 posi and break them. Open rear 57s got the slightly longer standard axles. This difference ended for the 58 model year and so for 58 and up all of the axles are the same length and can be used in either open or posi rears.

    Now, to install a Dana 44 style posi in a rear assembly that originally was an open rear, you need to shorten the axles. One way to tell, there is a raised area on the end of the standard open axles where the splines end. If that bump is present, you have unmodified axles and will need to grind that down. Posi axles for 57s are pretty rare as the posi option was not offered until a bit later in the production,maybe like December 56, so three months into 11 month production. I just did that very thing this past weekend when we installed my son's posi into his 57 rear.

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    hey there, Drag 6, thanx for the info, it`s me, "HDDUDE", upthe road from you.

  8. #8
    Registered Member Dragsix's Avatar
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    Hey there my friend! Like I noted, Patrick and I just shortened his axles for the 4 door sedan he is working on. If you post a photo of the ends of the axles, I can probably tell if they have been shortened. Like I said, real posi axles for a 57 are pretty rare. In fact, in the 43 years I have been messing with these cars, I have never had in my hands, or for that matter, even seen, a real 57 posi axle.

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    these are moser`s, made for `57 posi

  10. #10
    Registered Member Dragsix's Avatar
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    You have the same axles that I have then. You can run them for the posi or the open rear, no issues. But for anyone who has stock axles, see the little raised area above the splines, You grind that down flat and dress the sharp edges down and you are all set to use them with a Dana 44 style stock posi.

    dont go further, the original design of the Two piece Posi side gears will not get enough spline if you cut more. If you are running the newer style reproduction one piece posi side gears the amount you cut is not so critical.

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    Last edited by Dragsix; 09-17-2020 at 07:44 PM.

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