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Discussion Starter #1
Hey Guys,

Anybody know of a way to find out what the original factory rear axle would have been? Currently restoring my 1965 GTO which was purchased brand new by my Grandpa. Everything is original except for the rear axle and differential.
Originally was a Safe-t-track but was replaced with a standard rear end after he cracked the casting. Not even sure what the original ratio was. I know there was about seven options. Currently looking at an original 10 bolt Safe-t-track with a 3.08 ratio.
 

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you could at least narrow the choices down by knowing what transmission it came with.you need phs to be positive.
 

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DItto on the PHS docs. They will tell you exactly what rear end the car came with. For 1965, the 3.23 gear ratio was the standard issue ratio for both stick and auto and is the most common.
 

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Discussion Starter #5
No don't have PHS Docs. I see on line they are $65. I will get these ordered up right away. The 3.08 ratio does'nt sound right for the M20 4 speed. Possibly from an automatic?
 

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i personally like the 3:55 with an m-20. its real nice. im pretty sure the 3:23 was popular with 3 speed man. trans. popular 4 speed choices were 3:55 and 3:90. and a special order ballsy 4:33 LOOGOUT !!
 

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Discussion Starter #7
Well I'll keep my fingers crossed till the PHS doc comes. Never know, Grandpa did have a big foot.
 

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3.08 did come with M-20 equipped 4 speed cars. It was the highest gear you could get with a stickshift. Not a bad choice with $4 gas these days, either, if you want to drive the car. 3.23 is my all around personal favorite ratio for a 4 speed car. Plenty of power everywhere, and still fine on the freeway. I used to run 3.55's way back when, when the speed limit was 55...but now, I run 3.36's in my own '65. 3.55's are good for about a 60mph cruising speed, 3.36's will let you cruise 70 at around 3000 rpm. 3.08s, even better. Good luck with your project!!!
 

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Discussion Starter #9
Thanks for the info Geeteeohguy. Good stuff! I'm going to pick this one up anyway, even if I don't use it. To good of a deal and in excellent shape. Somebody can use it if I don't.
 
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