# **Help** Rear End Gear Ratio 1967 Goat



## Oldsmobileman (Dec 8, 2008)

Hey everyone I am trying to prepare for the "long haul" drive to Charleston, West Virginia This June. I will be driving from Sarasota, Florida to the convention. I have some pretty low gears in there now (haven't pulled them as of yet) but it sounds like a School bus between the tranny and the rear end. I just want to make it long distance without harming the rear end or motor from that many hours of high rpms. Looking for a good set of 4th gear cruising gears. Any recommendations would be welcome.

The car is a 1967 GTO 4 speed 400.

Thanks, Howard.

And if anyone wants to Convoy let me know.


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## Rukee (Feb 8, 2007)

3.55s or lower(number not gear ratio) would work great. Do you know what ratio you have now? To determine, if it's a posi unit, raise the tires off the ground, rotate the tires one full revolution and count the # of times the drive shaft turns. That is your ratio. If the drive shaft turns 4 and just a bit more, then that would be 4.10 gears.
If it's not a posi unit and only one tire turns, then turn that one tire two full revolutions and again count the # of times the drive shaft turns to get the ratio. Report back what you have.


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## geeteeohguy (Feb 2, 2008)

Howard, it sounds like you have a stick car. My advice would be to determine what gear is in there now, and go from there. My personal experience has lead me to prefer a 3.23 gear for stick GTO's, as it lets you cruise at 70mph at around 3000 rpm, and provides good off the line accelleration, as well as reasonable fuel economy. I recently changed from a 3.36 gear to a 2.56 gear in my '67 convert, (automatic car) and where it used to be 68-70mph at 3000 rpm, now it's 92mph at 3000, and 2450rpm at 75mph. It is slower off the line, not as snappy in town, but over 30mph, I love it. I drive this car on long trips, and I've gotten close to 20mpg with it. See the sticky thread on gears in this forum. Lots of information. The tallest gear Pontiac provided with a stiskshift GTO was a 3.08. That would be about the longest-legged I'd think of going with a 4 speed. You need to know what carrier you have, as well, as it will determine what gear you can replace your present gear with. There are 3 carriers: 2 series, 3 series, and 4 series. The gears dont' interchange. If all of this fails, you could forget about the gears, keep your speed at 50mph, and enjoy the scenery!!


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## Eric Animal (Oct 28, 2007)

Hey Howard! Long time no see! Eric:cheers


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## Oldsmobileman (Dec 8, 2008)

Thanks everyone for the help, and whats up Eric! All is good here except for a little rear end trouble. I was planning on pulling it down and doing an inspection before the trip, but then a want turned into a need. Wheel bearing was bad on one side and going out on the other. So we removed the axle shafts and pressed on the new bearings and gave the rear a full service. When I counted the gears there were 39 big teeth and 10 small teeth on the other. The rear is a 10 bolt. My friend said that should be a 3:90. Does that sound right? I will look tomorrow to see the casting number.


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## ppurfield001 (Jan 21, 2008)

Oldsmobileman said:


> Thanks everyone for the help, and whats up Eric! All is good here except for a little rear end trouble. I was planning on pulling it down and doing an inspection before the trip, but then a want turned into a need. Wheel bearing was bad on one side and going out on the other. So we removed the axle shafts and pressed on the new bearings and gave the rear a full service. When I counted the gears there were 39 big teeth and 10 small teeth on the other. The rear is a 10 bolt. My friend said that should be a 3:90. Does that sound right? I will look tomorrow to see the casting number.




Or..........you could run 3.55:1 gears in the back and install a 5-speed Keisler manual tranny. That way you can cruise at 1,850 RPMs on the highway at 70 MPH or greater. Good luck.


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## geeteeohguy (Feb 2, 2008)

39 teeth and 10 teeth = 3.90 ratio. You can bolt a set of 3.36 gears into your carrier and be all set. (if you can find the gears). 3.36 is as long-legged as you can go with your 4-series carrier. I made the same exact swap many years ago in a stick GTO (I was lucky enough to find a set of excellent gears). Changing the 3.90's to 3.36's made a useable car out of it. I'll take a 70mph cruising speed over a 50mph cruising speed any day of the week.....


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