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That little 327 is probably going to need a lot of gear, especially if it's been 'cammed'. You're also going to need some way to retain the axles in the housing - grooves on the ends for the clips, c-clip eliminators, or provisions for the backing plate/bearing retainers on the outboard ends of the housing.

Bear
 

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Sooooo.........what do you mean by "a lot of gear". Do you think 3:42 is too much power, not enough speed at the end or too much top end and not enough take off. And i kinda figured i was going to have to buy new c clip axles. Was hoping there was a way around it but if i have to, i will
 

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Sooooo.........what do you mean by "a lot of gear". Do you think 3:42 is too much power, not enough speed at the end or too much top end and not enough take off. And i kinda figured i was going to have to buy new c clip axles. Was hoping there was a way around it but if i have to, i will
Know what is in the engine and what the cam power range is is what can be used to determine your rear gears.

Small blocks can easily be built to push 7,200 - 7,500 RPM's all day long with forged parts, the good heads, and a cam that will begin pulling in the 3,500 RPM range. This would also require high compression and race gas - don't look to this engine for gas mileage.

So, 3.42 could be too low with a hot small block where it needs no less than a 3.73's and may do better with 4.11, 4.56 gearing to keep it happy. 3.42's could bog the engine if it has the higher RPM capabilities tied in with the cam.
 

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Sooooo.........what do you mean by "a lot of gear". Do you think 3:42 is too much power, not enough speed at the end or too much top end and not enough take off. And i kinda figured i was going to have to buy new c clip axles. Was hoping there was a way around it but if i have to, i will
No one can get specific without knowing a ton of detail about how your car is set up, but in general, little chevys don't make much low rpm torque to start with and 'big' cams only make that worse.

Like PJ said, I'd it's "built right" it can be pretty comfortable running high rpm, and 'shorter' gears help with that.

Bear
 

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Gotcha!!!! Well.......at this point, there is no turning back. I stumbled blindly into the carrier, ring and pinion and all bearings and seals for $150. Whats back there now is like a 2:76 which is ungodly fast once you get past the 0-60 time of approximately 10 days. So ill get it all hooked up with the v-gate ramrod shifter i ordered today and if it doesnt work out i may be able to put 3:73s right in that same carrier. Ill be sure to let you guys know how it works and i really appreciate the opinions, im new at this stuff!!!!!!
 

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My 69, 3:23, th400, 275/35/18's
 

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Hi. I'm posting a new thread because I didn't want to hijack another thread that this subject came up on: Gear ratios. I was bragging about my "racing" days, and gear ratios were mentioned. The following is some information that I have learned over the years, and the following opinions on gear choice are my opinions and nothing else. I am no engineer. I've run GTO's over the years with ratio's from 2.56:1 to 4.56:1. Stock early GTO's with stickshift usually came through with 3.55 gears, and aut0 cars had 3.36 gears standard. The 3.55 (4-Series) carrier could accomodate gears from 4.88 or so down to 3.36. The 3 series carriers could accomodate gears from 3.23 down to 2.51. I found that "back in the day", with cheap gas and road noise a fact of life, the 3.55 gears were okay.....the '66 tended to be running about 3200 rpm at 70mph....right in the power band. The speed limit was 55 at the time.Top end was ok. Low end was great. Good "all around" gear, back then. Now, 3200 rpm at 70 is too darn high. Too much noise, too much fuel, and with a big block Pontiac, uneeded. I ran a 3.90 gear in a '65 for a while. That car HATED the hiway. Top end was 107 mph, at redline. It would get there really quick, though. I changed out those 3.90's with a 3.36 gearset (the tallest gearset I could run in my 4 series carrier) back in 1990. Changed the car. Now, it loves 70 mph. It feels just about as strong out of the hole (Still can't hook up....tire smoke central), my fuel economy went way up, and my road noise went way down. I had another '65 with a 3.23 gear and a 4-speed, and the 3.23 is my FAVORITE gear ratio for these cars. It does everything well: accellerate, cruise, and top end. I drove a '65 with a 2.56 gear. GREAT top end, doggy as hell off the line. Too extreme. A friend had a 2.93 gear in his '67. The car would kick down into 2nd gear (turbo 400) at 85-90 mph. We smoked a 427 '65 Corvette on the hiway one day....he was running 4.11's and was done at around 105mph. The '67 would top 140 mph, I'm sure. Another friend had a 4.88 geared, dual quad 455 '66. We broke the wheel studs on the rear wheels getting on the freeway one day. He jumped on it, and there we were. The car would lay rubber when you got on it at 65mph., in 4th gear. Scary. cruising speed was 55 mph. Got about 8mpg at 55! My convertible '67 has the stock, 3.36 gearset. I wish it had a 3.23. It is a little busier at speed than I wish it was. I guess I'm getting old...I like running at 75 mph with minimum road noise and fuel consumption. Today, there's a lot of options with overdrives, lock-up converters, etc. If you want to modify your GTO and add a 700R4 trans, or add a 5 or 6 speed stick, you can run a 3.55 or 4.11 gear and STILL cruise at high speeds. If you're like me, and don't want to cut up your original old Goat, you have to choose what gear ratio best suits YOUR needs. For this guy, it's 3.23's.
Jeff
Still a great post after all these years. But.... You kind of cast doubt with your statement about "big block Pontiac". LoL
 

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Still a great post after all these years. But.... You kind of cast doubt with your statement about "big block Pontiac". LoL

Holy chit Batman! geeteeohguy must have been smoking those left handed California cigarettes that day because he certainly knows better. Can't believe we missed that one. Someone wash that man's mouth out with some Chevy big block wheel bearing grease and whack his pee-pee. (y)

"Too much noise, too much fuel, and with a big block Pontiac, uneeded. I ran a 3.90 gear in a '65 for a while."
 

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Interesting thread and thank you. Brings back fun memories. I owned a 66 GTO convertible that I put together back in ‘78-81. The shell was from someone the raced it on an oval. I put in a 389 and a turbo 400 in it both of which I rebuilt from the block and xmission case. It came with a 2.56 rear. The frame I think was twisted as it needed spacers on one rear wheel. Got a lot of tickets. Off the line it couldn’t get out of its own way. But given 5 miles I could pass anyone at very scary speeds. Speedometer was never right but that was not a good defense in court against the speeding tickets. The memorable moment was when another GTO passed me on the highway and I was with my girlfriend so I couldn’t let that happen. Caught up with the GTO after a while and the tach wasn’t even straining. Blew by him like he was standing still and the wind from passing lifted the hood and the radiator support bracket which dropped it into the fan. Ooops. Impress the girlfriend…..not. And the other GTO cruises by. Yup young and dumb. Lived to talk about it. I couldn’t keep axle bearings in it or tires on it. Ended up selling it for $800.
 

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I'm trying to figure out this gear ratio thing, Rukee. If I am going 70 mph on the highway, my 400 cubic inch engine is at about 3200 RPMs. Is that similar to your story above and, if you can venture a guess, what kind of gears am I running?
Just came back from a cruise today on a parkway with my wife following me at 70 mph tach was at about 3200 and gear ratio is 3.42 in 72 lemans. Hope this helps.
 

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My 67 has 2.93 gears....doggy off the line great top end..by todays standards it still feels like it needs another gear (TH400)....I was thinking of a set of 3.73 with a 4spd auto..200r4 can be built to take some torque. It is also an easy swap ....shorter yoke on the drive shaft..and a kit to adapt the his/hers.............Cool Thread
with 2.93 u need another gear on the hiway lol
 
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