Rear end ID codes have me confussed - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 10-23-2016, 12:49 AM Thread Starter
 
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Rear end ID codes have me confussed

OK so I Have more codes than I think I should.. I have a 68 with WF stamped twice on RIGHT side tube, when I thought it was supposed to be on the left. Also on the top tube RIGHT side about an inch out from carrier is stamped 337D. Now on the LEFT side tube same top area about an inch out is stamped either 354A or 364A. From what I have gathered I have a standard style with 3.23-1 gearing. Also I have seen info both ways saying its a 65 rear end and I have seen it called a 68. Can anyone expalain please
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post #2 of 5 (permalink) Old 10-23-2016, 09:14 AM
 
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The two letter ID code WF was used on several years of Pontiac 8.2 rearends, so can't just ID from that alone. In identifying Pontiac 8.2 rears or Buick 8.2 rears, when identifying these early bolt in axle A body rears, I usually first look at the casting number cast in the lower webbing of the center housing, then look for the cast alphanumeric date in lwr webbing. The I start cleaning axle tubes, looking for original stampings. Pontiac 8.2 center housing casting #'s will begin with a casting number of 97xxxx. There were easily 15 of these center housing casting numbers from '64-72, just for Pontiac 8.2 center housings. The casting number of thr early Buick 8.2's ('64-67) will begin with a 5. Looking at the side of the cast center housing, the Buick 8.2 gray iron center housings will not have the twin converging ribs on the sides of the center housing extending down to the the pinion area like that of the Pontiac 8.2's.

The early style Pontiac 8.2 rears, & early Buick 8.2 rears, both rears, can be further ID'ed by their width. On early A body rears, one will only be able to get one finger on the axle tube between the outer edge of the shock mounting bracket & the plane of the brake backing plate. For '66 & later models* the bolt in axle A body rears were widened slightly (aprox 1/2" each side). With these later A body rears, one can slip two fingers between the outer edge of the shock mounting bracket and the brake backing plate.

There is another identifying feature of the first 3 years production of GM A body rears. The rear coil springs are retained by bolt on spring retainers. These "ear shaped" stamped steel retainers clamped the bottom pigtail of the '64-66 rear coil spring to the perch. '67 & later production A body rears had coil spring perches that the center area protrudes upward & locates the larger diameter lower pigtail of the coil spring, no bolt on retainers, at least from the factory.

The center housing casting number & the cast date on that center housing basically lock in the original usage of an original rearend. Single letter, 2 letter or 3 letter ID codes stamped into an axle tube along with the the factory assembled day of the year, should be present, but many times these stamped codes are illegible. Also have to remember, some folks like to play around stamping their own axle tube codes. Usually, on Pontiac 8.2 rears, as well as 12 bolts, I can spot the wrong font of stamped lettering. Some original styles of GM rears, however, the stamping of the ID code was not "picture perfect". Having personally built many GM rears, where I setup different ratio of gears, its never smart just to trust a stamped ID code. Instead, wise to remove the rear cover, drain the grease, & look at the ring & pinion, Factory gear sets will have a date inscribed, as well as a ratio code, ex: 39 11 in the side of the machined edge of the ring gear would note a 3.55. aftermarket gears sets, one can count the teeth on the ring & pinion, then a little simple math. Hope this helps.

* Note, a very few very early production '66 Pontiac A body's have been parted which have been documented to have date matching late '65 production "narrow" Pontiac 8.2 rear-ends
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post #3 of 5 (permalink) Old 11-29-2016, 03:05 PM
 
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Originally Posted by Pinion head View Post
The two letter ID code WF was used on several years of Pontiac 8.2 rearends, so can't just ID from that alone. In identifying Pontiac 8.2 rears or Buick 8.2 rears, when identifying these early bolt in axle A body rears, I usually first look at the casting number cast in the lower webbing of the center housing, then look for the cast alphanumeric date in lwr webbing. The I start cleaning axle tubes, looking for original stampings. Pontiac 8.2 center housing casting #'s will begin with a casting number of 97xxxx. There were easily 15 of these center housing casting numbers from '64-72, just for Pontiac 8.2 center housings. The casting number of thr early Buick 8.2's ('64-67) will begin with a 5. Looking at the side of the cast center housing, the Buick 8.2 gray iron center housings will not have the twin converging ribs on the sides of the center housing extending down to the the pinion area like that of the Pontiac 8.2's.

The early style Pontiac 8.2 rears, & early Buick 8.2 rears, both rears, can be further ID'ed by their width. On early A body rears, one will only be able to get one finger on the axle tube between the outer edge of the shock mounting bracket & the plane of the brake backing plate. For '66 & later models* the bolt in axle A body rears were widened slightly (aprox 1/2" each side). With these later A body rears, one can slip two fingers between the outer edge of the shock mounting bracket and the brake backing plate.

There is another identifying feature of the first 3 years production of GM A body rears. The rear coil springs are retained by bolt on spring retainers. These "ear shaped" stamped steel retainers clamped the bottom pigtail of the '64-66 rear coil spring to the perch. '67 & later production A body rears had coil spring perches that the center area protrudes upward & locates the larger diameter lower pigtail of the coil spring, no bolt on retainers, at least from the factory.

The center housing casting number & the cast date on that center housing basically lock in the original usage of an original rearend. Single letter, 2 letter or 3 letter ID codes stamped into an axle tube along with the the factory assembled day of the year, should be present, but many times these stamped codes are illegible. Also have to remember, some folks like to play around stamping their own axle tube codes. Usually, on Pontiac 8.2 rears, as well as 12 bolts, I can spot the wrong font of stamped lettering. Some original styles of GM rears, however, the stamping of the ID code was not "picture perfect". Having personally built many GM rears, where I setup different ratio of gears, its never smart just to trust a stamped ID code. Instead, wise to remove the rear cover, drain the grease, & look at the ring & pinion, Factory gear sets will have a date inscribed, as well as a ratio code, ex: 39 11 in the side of the machined edge of the ring gear would note a 3.55. aftermarket gears sets, one can count the teeth on the ring & pinion, then a little simple math. Hope this helps.

* Note, a very few very early production '66 Pontiac A body's have been parted which have been documented to have date matching late '65 production "narrow" Pontiac 8.2 rear-ends
Great post! I think I learned more info about rear axles in this one post than all other sources combined. Thanks!

I think I will send you pics of my 68 ZF axle so you can verify if everything looks correct for my model. I think it's original to the car but it doesn't hurt to have someone else look it over to be sure. I won't be starting on chassis assembly until spring so it will be a few more months yet...

Sent from my XT1585 using Tapatalk
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post #4 of 5 (permalink) Old 04-21-2018, 09:02 PM
 
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Hi P-H, I've read your various posts on the forum and can't think of a better resource for my question. I am trying to determine what I have for a differential. I have two lines of code: "J4 5" and "9789393" and that is all I see on the tubing. Any thoughts?

Many thanks!
Michael
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post #5 of 5 (permalink) Old 04-22-2018, 08:56 AM
 
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Fairly early (Oct '65) dated '66 gray iron Pontiac 8.2 housing by the date & the housing number. Could have Pontiac or Olds usage two letter codes. Hope you have the bearing caps, so it can be reassembled. Have gone through the missing (previous broken) drivers side cap on several 12 bolt rears, even with having several 5 gal buckets full of 12 bolt caps, it's been a challenge to find a cap that properly fits.
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