[remy30006]

Could somebody explain what the difference is between the performance axle and economy I understand safety track is a posi but unclear about performance axle. My car is suppose to have both.

[Dick Boneske]

There is no such thing as a "performance and economy axle." There is a tradeoff--lower ratios (higher numbers) give better acceleration while higher ratios (lower numbers) give better economy.

The '64 GTO standard rear axle ratio was 3.55:1 early on and 3.23 later in the production year. The 3.55 ratio resulted in about 950 rpm per 20 mph of vehicle speed. So, at 60 mph in high gear, your engine would be running 2,850 rpm.

That's nearly double the engine speed on most modern vehicles, which results in more fuel usage, engine wear, noise, etc. The tradeoff was that the stock GTO's accelerated faster than most cars built in 1964. Their top speed was limited by engine RPM--120 mph would have the engine at 5,700 rpm.

The optional performance axle in a '64 GTO was 3.90:1, which gave 20 mph per 1,000 rpm.

[remy30006]

On my PHS documentation it has 3:23 gears and performance axle as well as safety trac.
Does that make sense?

[remy30006]

Dick,

I just noticed you are from Wisconsin, I am originally from Oshkosh now living just north of Appleton.

[geeteeohguy]

3.23 was not known as a performance axle. It was standard, as stated, in late '64 thru '66. If you had a non-ac car, and didn't specify, that was what you got. Safety Track was extra, and available in all gear ratios. I have seen Performance Axle on build sheets, and it is always a 3.90 or 4.33 ratio. An 'economy' axle is usually a 2.56 ratio. Not really seen on GTO's until '67, with the 2bbl economy engine.

[remy30006]

Thanks for the help just trying to understand the build sheet and what my car would have came with. My axle code is 9K which looks like 1 for safety trac 8 for performance axle and K for 3:23 axle. Are the PHS documents not very accurate?

Thank you again

[Tom Vaught]

Originally Posted by remy30006

Thanks for the help just trying to understand the build sheet and what my car would have came with. My axle code is 9K which looks like 1 for safety trac 8 for performance axle and K for 3:23 axle. Are the PHS documents not very accurate?

Thank you again

Typically very accurate for a Pontiac Plant Built vehicle.

Some options are not as accurate on the KC built vehicles because I am told by John V. that they used a different coding system. In 1964, the vin will have 824 "M" (Kansas City) GTO at the beginning vs 824 "P" (Pontiac) GTO.

Sometimes the options on the cars were different even though the coding was correct.
My 64 GTO says the car came with the 3.23 Axle and Power Brakes. Car never had Power Brakes from Day 1. The car was built with the 3.90 axle (as received by me) but that could have been changed as well as the speedo gear by the St Louis Zone Office.

But stuff happened in the plants. So I would not worry too much about EXACT documentation even though people would like to find as much stuff out about their cars as they can. I know my uncle (a Pontiac Dealer) several times installed options that were not built into the cars on the line but were ordered by the customer. He made the customer happy on his dime.

Tom Vaught

[b-man]

The 'economy' axle for 1964 would have been a 3.08 ratio for stick shift cars.

[remy30006]

so that would be correct to call 3:23 a performance axle? Thank you for the help and Merry Christmas to everybody, just trying to be accurate and understand the coding

Paul

[Tom Vaught]

If the 3.08 was the economy axle, the 3.23 was the STANDARD axle and the 3.90 was the performance axle, I think that would be more correct.

Tom Vaught

[64woodwheel]

Economy vs. Standard. vs. Performance is relevant to the application as this chart illustrates. Not very easy to read. I will try rescanning at a higher res and see if it helps.

[remy30006]

The chart is awesome info. Can I ask where to find charts like that. I still don't see where my coding lines up. My axle code is 9 k and it is GTO 4 spd locking rear and performance axle but it also states 3:23 gears, does the performance axle over ride the 3:23 or the other way around? Was it special order if so why would the build sheet still state this. I want to put the car back to as close to original as I can.

Thank you!

[geeteeohguy]

b-man just jugged my memory...I remember a 1964 GTO ad that said something like '...and fuel economy won't be anything to write home about, either, unless you order it with our lazy 3.08 gear..." So, yeah, in '64. I'd buy the 3.08 as an economy axle in a heartbeat.

[Kenth]

1964 GTO IS a Performance option on the Tempest.
No such thing as a Performance rear axle option for this car.

Code 9 was only used for Fullsize vehicles.

A 1964 GTO w/4-speed would come with a 3.23:1 rear end, code 2K open diff, code 3K Safe-T-Track.
With metallic brake linings code 2L open diff, code 3L Safe-t-Track.

You could "Special Order" 3.08:1, 3.36:1 and 3.55:1 ratios open or Safe-T-Track standard brakes and 3.36:1, 3.55:1 and 3.90:1 ratios open or Safe-T-Track w/MB except 3.90:1 only Safe-T-Track.

Add to those the Dealer installed Safe-T-Track 4.11:1, 4.30:1 and 4.33:1 ratios.

Info from the 1967 Pontiac Chassis Parts Catalog Rear Axle Usage and Identification Chart.

[remy30006]

This is the paper work that came with the car that states 9 K for the axle code the other papers have performance axle high lighted and safety track high lighted as well as 3:23 gears, Unless it is inaccurate or not valid. Also the option sheet states 701 is safety trac 708 is performance axle which make the 9 and k=3:23. Just trying to understand.

I did try to scan the high lighted sheets but they didn't come through.

Thank you!

[64woodwheel]

I think your PHS report is correctly decoded. Code 70(9) is 701 Saf-T-Track and 708 Performance Axle Preference combined. 71(K) denotes the K ratio, 3.23:1. I am not sure of the rational of coding them as performance pref. If you ordered a 6 cyl. Tempest with V82 trailer provisions, a 3:90 would have been coded as standard. Without V82, a 6 cyl. automatic with a 2.93 would be coded performance. Code 9 as applied to transmissions was stamped on the engine block (even 6 cylinders) by the assembly plant and only used for 3 and 4-speed applications with 3.73 or numerically higher gears. It has nothing to do with close ratio 4 speeds as some believe.

[remy30006]

So maybe performance axle is a misnomer? Where on the engine would the number 9 be stamped for a 4 speed? In the production code? If it came with a 4 barrel 4 speed would it be a 78x or 78w engine?

Thank you!

[64woodwheel]

The numbers are stamped on the front of the passenger side by the timing cover.

[remy30006]

I see the w so 78x w but where is the x9 stamping? Also what does the sm as in x-sm (3speed) mean?
Thank you this is great info.

[johnta1]

what does the sm as in x-sm (3speed) mean?

Sm = manual transmission.