Author Topic: puzzling 3rd member tag  (Read 2479 times)

acman63

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puzzling 3rd member tag
« on: April 01, 2020, 09:16:42 PM »
I recently acquired a totally greasy 3rd member and when I had it cleaned came up with this tag 

C5GA-D    4L11  5CB   SP  so far the 4L11  checks out for ratio and limited lip  .  date corresponds with the casting date on the case.  im puzzled by the Tag  ID  none of my books show this number. Looks like a Mercury Comet type engineering . number to me
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Royce Peterson

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Re: puzzling 3rd member tag
« Reply #1 on: April 02, 2020, 09:26:43 AM »
Jim I think what you have there is the tag for something rare like a '65 Comet with 427, or perhaps one of the SOHC Mustangs produced in '65. The plant code "SP" indicates a special build, likely only a few assemblies made. They did not even bother to assign the assembly one of the "W" codes, instead just putting the part (or maybe engineering) number on the tag.

I checked my Mercury Master Parts Catalog and also did not find any reference to the number on your tag. There may be a drawing in existence still at Ford P/N C5GA 4200-D.


I recently acquired a totally greasy 3rd member and when I had it cleaned came up with this tag 

C5GA-D    4L11  5CB   SP  so far the 4L11  checks out for ratio and limited lip  .  date corresponds with the casting date on the case.  im puzzled by the Tag  ID  none of my books show this number. Looks like a Mercury Comet type engineering . number to me
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock

gt350hr

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Re: puzzling 3rd member tag
« Reply #2 on: April 02, 2020, 11:57:00 AM »
   It is NOT from an A/FX (SOHC) Mustang or Comet because it has a 28 spline Equal lock AND it is NOT a Nodular iron case. The 4.11 ratio was available as an option in the '65 Full size Mercury( w/427)and Cyclone as well as equalock. The B/FX Comets used the same setup as the A/FX cars , not 28 spline stuff. The tags on A/FX differentials began with DSO like SAI vehicles did. I had a few of the original A/FX tags I got from the late Dynp Don (rip)
     Jim , remember that MANY '65 GT350s had a C5ZA numbered tag that didn't appear in the MPC. "I" believe this combination was an infrequent order ( made to order , not "stocked") and not enough to be listed in the L-M MPC as Royce noted.
     Randy
« Last Edit: April 02, 2020, 12:19:35 PM by gt350hr »
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acman63

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Re: puzzling 3rd member tag
« Reply #3 on: April 02, 2020, 12:49:24 PM »
i checked and its 28 spline .   
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gt350hr

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Re: puzzling 3rd member tag
« Reply #4 on: April 02, 2020, 01:48:19 PM »
   And standard single rib case , right?
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Royce Peterson

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Re: puzzling 3rd member tag
« Reply #5 on: April 02, 2020, 01:48:56 PM »
Maybe a 289 HP Comet or Fairlane if it is a 9" 28 spline with Equa Lock.


   It is NOT from an A/FX (SOHC) Mustang or Comet because it has a 28 spline Equal lock AND it is NOT a Nodular iron case. The 4.11 ratio was available as an option in the '65 Full size Mercury( w/427)and Cyclone as well as equalock. The B/FX Comets used the same setup as the A/FX cars , not 28 spline stuff. The tags on A/FX differentials began with DSO like SAI vehicles did. I had a few of the original A/FX tags I got from the late Dynp Don (rip)
     Jim , remember that MANY '65 GT350s had a C5ZA numbered tag that didn't appear in the MPC. "I" believe this combination was an infrequent order ( made to order , not "stocked") and not enough to be listed in the L-M MPC as Royce noted.
     Randy
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock

gt350hr

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Re: puzzling 3rd member tag
« Reply #6 on: April 02, 2020, 02:31:20 PM »
  Comet. Probably  D engine code HiPo Cyclone.
    Non standard , but still RPO diffs used a "low production" tag # in this case C5"G"A noting L-M destination.  A Galaxie tag was C5AA  , and as I mentioned '65 GT350s were C5ZA . I have not seen a C5OA tag , "yet". Common production ratios used the familiar WCZ , WFD etc type prefixes well documented in the MPC. When I was factory trained to do differentials in '68 I knew most of the codes by heart. Now I have to look them up except for the oddball ones. I have a hand written log book of those including many of the XW numbered "race differentials".
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Royce Peterson

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Re: puzzling 3rd member tag
« Reply #7 on: April 02, 2020, 03:00:53 PM »
While the part was originally paid for by Comet engineering the part would have been used in any other application that needed the same specs. So you often see for example engineering paid for by full size Ford or Mercury but the components then show up across the board. That's why if this part was used for a 289 HP Comet it would also be used in a Fairlane or even a Mustang or Shelby if the demand for the same design existed.

  Comet. Probably  D engine code HiPo Cyclone.
    Non standard , but still RPO diffs used a "low production" tag # in this case C5"G"A noting L-M destination.  A Galaxie tag was C5AA  , and as I mentioned '65 GT350s were C5ZA . I have not seen a C5OA tag , "yet". Common production ratios used the familiar WCZ , WFD etc type prefixes well documented in the MPC. When I was factory trained to do differentials in '68 I knew most of the codes by heart. Now I have to look them up except for the oddball ones. I have a hand written log book of those including many of the XW numbered "race differentials".
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock

gt350hr

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Re: puzzling 3rd member tag
« Reply #8 on: April 02, 2020, 05:11:59 PM »
   Not in this case as it wasn't a "generic" differential. If it was you would have found it in the L-M MPC. BTW "SP" is for the Sterling axle plant , not "special". Ford also assembled the majority of drivetrain components in Wayne.
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Re: puzzling 3rd member tag
« Reply #9 on: April 04, 2020, 01:34:51 PM »
Disagree because it is not a generic differential - it was used only under some very special circumstances hence it did not appear in any MPC. If anyone knows someone in building 2 they could pull the print and find out what it was used in.


   Not in this case as it wasn't a "generic" differential. If it was you would have found it in the L-M MPC. BTW "SP" is for the Sterling axle plant , not "special". Ford also assembled the majority of drivetrain components in Wayne.
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock

gt350hr

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Re: puzzling 3rd member tag
« Reply #10 on: April 06, 2020, 10:53:45 AM »
    REREAD my post , I said it wasn't a generic and I explained why. Save yourself the time on having it looked up. Bob Mannel's Small Block Ford book shows a build sheet for a '65 Comet "A" engine code but noted at the bottom as a HiPo. The rear axle assembly code is C5GA. Proof enough for you?
 Now for those that don't know , the tag we are referring to is for the entire rear axle assembly , from drum to drum. So , for instance in the case of a '66 GT350 the C5ZX ( carryover) or C6ZX  tag was used to note it was different ( brakes only) than a normal WCZ HiPo 9" axle assembly. While changes to the third member "could" be the reason like the one Jim asked about , "other" changes can be the reason for a special tag.
    Randy
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Royce Peterson

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Re: puzzling 3rd member tag
« Reply #11 on: April 08, 2020, 04:37:33 PM »
Indeed great proof it was installed on that car. Not proof that it was not used in other applications.

    REREAD my post , I said it wasn't a generic and I explained why. Save yourself the time on having it looked up. Bob Mannel's Small Block Ford book shows a build sheet for a '65 Comet "A" engine code but noted at the bottom as a HiPo. The rear axle assembly code is C5GA. Proof enough for you?
 Now for those that don't know , the tag we are referring to is for the entire rear axle assembly , from drum to drum. So , for instance in the case of a '66 GT350 the C5ZX ( carryover) or C6ZX  tag was used to note it was different ( brakes only) than a normal WCZ HiPo 9" axle assembly. While changes to the third member "could" be the reason like the one Jim asked about , "other" changes can be the reason for a special tag.
    Randy
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock

gt350hr

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Re: puzzling 3rd member tag
« Reply #12 on: April 09, 2020, 02:51:23 PM »
   So prove it WAS used elsewhere. I showed you where it was used , now it's your turn. WCZ , WES , WFD , no problem , they were "generic". C5ZX , C6ZX , C7ZX ,C8ZX, C5ZA, C5GA, C8AA, and MANY more were specific and not used elsewhere. NONE of these are found in ANY MPC. These were typically assembled at the Sterling axle plant SP which you assumed was "special" however generic axle assemblies was also built there as can be seen on "W" series axle assemblies that have the SP on the tag. If you need visual proof of that I have MANY generic tags that ARE in the MPC with the SP on them. I asked the question 52 years ago at the Ford Motor Company differential training class I was attending when we were on the subject of ''warranty tags". That is what the instructor told me. I still have the notes in my '68 training books.
    Randy
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