'66 differential? - Pontiac GTO Forum
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post #1 of 8 (permalink) Old 04-21-2018, 08:24 PM Thread Starter
 
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'66 differential?

Hi Folks; I was hoping that someone could tell me what gears I have or even if I have an original GTO differential. The numbers I have on the differential do not match anything that I have found on the web. With my bad eyes it looks to be "J4 6" with "9788393".

Any help would be greatly appreciated!

Cheers
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post #2 of 8 (permalink) Old 04-22-2018, 05:23 AM
 
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Garage
It is a '66 but you need to locate the two letter code that should be on the RH axel tube to see what gear set was installed originally,
right of the vent on the rear facing out on tube is where they are commonly stamped.
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post #3 of 8 (permalink) Old 04-23-2018, 09:07 PM
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How many teeth do you have on the ring and pinion gears?

Randy


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post #4 of 8 (permalink) Old 04-24-2018, 05:07 AM
 
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The one shown above was a 3:55
My '66 with AC has a 3:23
here it is before re-assembly many miles ago, don't recall tooth count.
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post #5 of 8 (permalink) Old 04-28-2018, 08:47 PM Thread Starter
 
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Hey guys, thanks very much for your help. Those alpha codes are small, I think I may have gone right over them without noticing! I did count the gear teeth and came up with 42 and 13; 3.23 ratio?
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post #6 of 8 (permalink) Old 04-28-2018, 08:49 PM Thread Starter
 
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I guess my other question would have to be around the type of rear-end. Is it a posi or not?
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post #7 of 8 (permalink) Old 04-28-2018, 09:30 PM
 
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Oem 8.2 Pontiac Safe-T-Track (posi) carrier. All oem Pontiac 8.2 STT carriers were cone type, hopefully cones have not bottomed out and carrier is no longer tight. If considerable wear on the cones will need disassembly, machining, shimming up, and reassembly.
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post #8 of 8 (permalink) Old 04-28-2018, 09:37 PM Thread Starter
 
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Hi PH, thanks very much! Unfortunately as a real dummy/newbie, I really dont know what you mean by cone type? How do I tell if they are bottomed out and need machining? Regards
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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