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Old 08-21-2020, 01:45 PM
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Default "69 Grand Prix rear end gear ratio

My GTO has a rear axle from a '69 Grand Prix. Have had a deficult time finding the code on the rear axle tubes to determine the rear axle ratio.

Are the codes on the GP axle in the same place(s) as on the '69 GTO's axles?
Thanks in advance.

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Last edited by 1968GTO421; 08-21-2020 at 01:46 PM. Reason: typo
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Old 08-21-2020, 02:58 PM
694.1 694.1 is offline
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Short of a code, it is easy to determine the ratio. Is it a limited slip?

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Old 08-21-2020, 03:21 PM
'ol Pinion head 'ol Pinion head is offline
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Drivers side axle tube, stamped a little high. Same plane as the coil spring perch but on the rear side of car. With car on jack stands, can be seen from rear of the car, if not stamped too high.

Have parted quite a few '69 GP's, more SJ's than Model J's. Codes as follows.

2D or 4D 2.93 peg leg (typical 400 auto w a/c)
2F 3.23 peg leg
2F or 4F 3.23 pegleg

5D 2.93 STT

4 pinion Safe-T-Tracks:
5F 3.23
7G 3.36
7H 3.55
7K 3.90 (have never had one in my hands)

Have a few bare '69 GP housings coded 5F,
clean Southwest housings, can provide dates. cheap.

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Old 08-22-2020, 11:35 PM
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Here's two photos of the code location from a '69 GP I owned years ago, hopefully this will help. This was on the driver's side behind the coil spring and just above the brake line looking from the rear of the car.
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Old 08-23-2020, 01:49 PM
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Quote:
Originally Posted by 694.1 View Post
Short of a code, it is easy to determine the ratio. Is it a limited slip?
It has a small metal tag on one of the cover retaining bolts that says " limited slip' use proper fluid". Those aren't the exact words but close.

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Old 08-23-2020, 02:16 PM
'ol Pinion head 'ol Pinion head is offline
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The spot I mentioned earlier & 428ho4spd put pics up, is the same.

One thing about stamped rearend ID codes, quite a few times I've ran across a housing in a car that a previous owner thought it was cool to haphazardly stamp his own ID code on an axle tube after having another ratio gear set installed. With cheap commonly avail stamps with the incorrect font, & often stamped in the wrong spot, I used to shake my head. It happens, as do gear ratios get swapped without the owner "playing with stamps". As a result, I always pull the rear cover & check the gear set for ratio & condition.

Another, amusing deal w rears in the boneyards... years ago, harvesting 8.5 posi units in the cheap yards, several times I came across what had once been someone's pride & joy street machine, usually a terd mid 70's Camaro or Malibu, & it's rear gear had been changed to lower gearset. I crawl undrneath, pull the rear cover & caps, & voila... instead of a correct thickness cast steel spacer between the left carrier bearing race & the housing, & a GM service spacer & one or two thin GM shims on the passenger side, I'm treated to two thick stacks of thin aftermarket shims on each side. Once I pulled the axles, the preload on the carrier bearings was so loose, the posi w mounted ring gear would fall right out. Had to love it, as the pile of aftermarket shims would eventually come in handy.

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Old 08-23-2020, 07:27 PM
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Quote:
Originally Posted by 'ol Pinion head View Post
The spot I mentioned earlier & 428ho4spd put pics up, is the same.

One thing about stamped rearend ID codes, quite a few times I've ran across a housing in a car that a previous owner thought it was cool to haphazardly stamp his own ID code on an axle tube after having another ratio gear set installed. With cheap commonly avail stamps with the incorrect font, & often stamped in the wrong spot, I used to shake my head. It happens, as do gear ratios get swapped without the owner "playing with stamps". As a result, I always pull the rear cover & check the gear set for ratio & condition.

Another, amusing deal w rears in the boneyards... years ago, harvesting 8.5 posi units in the cheap yards, several times I came across what had once been someone's pride & joy street machine, usually a terd mid 70's Camaro or Malibu, & it's rear gear had been changed to lower gearset. I crawl undrneath, pull the rear cover & caps, & voila... instead of a correct thickness cast steel spacer between the left carrier bearing race & the housing, & a GM service spacer & one or two thin GM shims on the passenger side, I'm treated to two thick stacks of thin aftermarket shims on each side. Once I pulled the axles, the preload on the carrier bearings was so loose, the posi w mounted ring gear would fall right out. Had to love it, as the pile of aftermarket shims would eventually come in handy.
Gotta love it, just amazing what you find done with these old cars

Want to say Thanks for the good advice you've given and all the knwledge too. Despite my age, I've continued to learn a lot from you--Thanks.

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