How can I tell if these are HiPo Axles?

[5s127]

How can I tell if these are HiPo Axles? I purchased a 65 HiPo rear and I don't know if the axels are HiPo. One axel is a C4OW. I can't make out the letters on the other axel although they both appear to be the same other than the length.

[gt350hr]

   The C4OW axle IS the "improved version" over the C2OW axle. There isn't a "HiPo specific " axle as you are suggesting. As an FYI the "visual" difference is the lack of material conformity on the C2OW axle. There are "voids" or "low areas" in the forging itself. These voids led to axle failure in manual transmission applications. Ford did produce "some" 31 spline axles for factory race cars ( Thunderbolts and A/FX Mustangs) BUT they were NEVER an "assembly line" option on any 64-66 Mustang or Fairlane. These rare axles are a completely different forging.
     Randy

[98SVT - was 06GT]

Ford did produce "some" 31 spline axles for factory race cars

So Gas Ronda's Mustang broke one of the 31 spline axles? I wonder if the forging was bad and/or if the xrayed these parts back in the day.

[TA Coupe]

at a certain power level anything will break😱

         Roy

[6s1640]

   The C4OW axle IS the "improved version" over the C2OW axle. There isn't a "HiPo specific " axle as you are suggesting. As an FYI the "visual" difference is the lack of material conformity on the C2OW axle. There are "voids" or "low areas" in the forging itself. These voids led to axle failure in manual transmission applications. Ford did produce "some" 31 spline axles for factory race cars ( Thunderbolts and A/FX Mustangs) BUT they were NEVER an "assembly line" option on any 64-66 Mustang or Fairlane. These rare axles are a completely different forging.
     Randy

Hi Randy,

I am confused now.  According the Ford MPC, the 65-66 Mustang 9 inch rear end (C5OZ-4234-A/B) uses a different axle than the 8 inch rear end (C2OZ-4234/5-A.) In terms of their interface to the third member and the outer bearing, brakes and wheel, they are interchangeable.  But they are different or as you say the C4OW (C5OZ-4234-A/B)  is improved.  Because the C50Z-4234-A/B axles are unique to the 65-66 Mustang 9 inch, which only came on K-code HiPo 289 cars, seams to me that logic makes these axle HiPo.

Based on my assessment of the C5OZ-4235-A/B axles, using the formulas for strength and deflection, they are not any stronger (ultimate strength) than the C20Z-4234/5-A, but have less deflection when under load.  Less deflection could also improve their fatigue strength as well, making them seam stronger.  Is this the improvement?

Cory

[Relicdog]

There are 65-66 Mustangs with 8" rears that have C4OW axles, an
yes they are totally interchangeable with 8" or 9" rears.

[gt350hr]

Ford did produce "some" 31 spline axles for factory race cars

So Gas Ronda's Mustang broke one of the 31 spline axles? I wonder if the forging was bad and/or if the xrayed these parts back in the day.

     The Ronda failure was a combination of events. As you know these cars used Detroit Lockers . They have allot of "internal slack" AND in a drag race application have been known to be in an "unlocked" condition on manual transmission cars "on the starting line". It is "my" opinion this "slack condition" along with "sudden application" of 500+ ft lbs of torque caused an extreme shock load that "over time" caused the axle to fail. It probably twisted "some" before the ultimate failure. I had broken two left side 28 spline axles before I switched to 31 spline versions . Yes they are original 56 year old A/FX axles!
    Randy

[427heaven]

Would it be safe to say because of a few tragic incidents in that time frame, SPOOLS were the THING from there forward?

[gt350hr]

      Cory,
       The C2OW axle forging was created for the '62 Fairlanes with the 221 V8. This same axle was used in '63 when the 260 and 289 HiPo were introduced. Axle breakage became a problem in '63 so the C4OW axle was designed and used for "manual" transmission applications. Since the Mustang used the same axle lengths , the same axles were used. I have seen many original 3spd equipped (8" diff)  Mustangs with C4OW axles and mostly C2OW axles in automatic ( 8" diff) applications. ALL "K code" diffs had C4OW axles , regardless of transmission type.  The "uniform" ( and slightly larger) shaft design of the C4OW axle makes it FAR stronger torsionally  plus the lower deflection you noted. While the MPC notes that  axle for 9" applications it is not "exclusive" to them.
   Randy

[gt350hr]

Would it be safe to say because of a few tragic incidents in that time frame, SPOOLS were the THING from there forward?

        The spool reduces the "slack" to almost nothing. It is also always "locked" as there are no moving parts. It is STILL possible to fail the driver's side axle because it is shorter , reducing it's ability to absorb torsional loads compared to the longer passenger side axle. The "next steps" were larger , bigger spline axles. Now at 44 splines in all but Nitro applications which have had to go to a "live"( one piece) axle. Detroit lockers are still OK for automatic transmission drag cars as they are "power braked" , removing all of the internal slack in the unit.
  Randy
   

[Silver Bullitt]

Were the 65/66 Untappered axles identical to '65/'66 HiPo axles?

[gt350hr]

      No , the diameter of the axle shaft is larger all the way to the end . It is a bear to slip it through the stock ( small) seal without damaging it. They are several pounds heavier. They were also xray inspected for flaws.
    Randy

[mygt350]

side question. Is the side gear in a 28-spline 9 inch housing same outer diameter as a 31-spline side gear in same housing?
Will 28 and 31 spline axle gear fit in same half?

[pbf777]

Is the side gear in a 28-spline 9 inch housing same outer diameter as a 31-spline side gear in same housing?
Will 28 and 31 spline axle gear fit in same half?

     In my experience yes, as I have changed many a 28-spine carrier housing to 31-spline; but this does require boring the bearing support snouts up in diameter to allow the larger axle shaft to enter the carrier to engage the 31-spline side gear.     

     Scott.

[mygt350]

Hey Scott
If outer dimensions of a 28 and 31 spline side gear are indeed same, why does the bearing support snout need to be opened up to clear the larger diameter 31 spline axle?