[Oletrucks] Task Force Differentials

[MIQ MILLMAN]

Sorry for the late reply James.  I had to go through my paper archives from
when I modded my '57 3200.

Stock is 3.90:1 or 4:11:1 -- it depended on which transmission was
originally in the truck.

8.5" 10 bolts from '73 - '87 (Square Body) should fit.

I actually went a different route:  I put in a 1989 Camaro Z28 rear end,
that had both a posi-trac and disc brakes--this was a Borg Warner 9-bolt
with a 3:27:1 ratio-- this is also a smaller ring gear, 7.75, but was more
than adequate with my fuelie head/fenton headered/HEI 235 hotrod engine at
the time, especially since I also retained the 4 speed with granny 1st
gear..  I fixed the slight change in width by changing the offset on the
wheels I used.

In the drag world, the 9 bolt is sometimes considered to be a much superior
choice to the 10 bolt.  IF you go that route, make sure to get the 11 tooth
pinion/ 41 tooth ring if you go for the 3:73:1--it's much stronger than the
10 tooth pinion/37 tooth ring.


   --Miq



On Thu, May 16, 2024 at 11:20 AM James Wolford <jgwolford at aol.com> wrote:

> Hello all,
>
> I have a 1957 Chevrolet 3100 pickup.  It currently has an open rear end
> and I believe the gears are 390 or the same as the sedan.  I am wondering
> about replacing the center section with a posi unit and was wondering if a
> 8.5 would work?
>
> Thanks,
>
> Jim W.
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