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Discussion Starter #1
Drove my 67 GTO from western CT to central CT. First leg was 1.5 hours and all highway. That was not fun. Engine temp would hold steady at 200 as long as I didn't go over 50 mph (Speedo said 85 mph). Anything over 50 mph and the temp would start climbing on me.

Second leg was two-hours of off-highway driving to a shop for a rear diff swap (ditching the 4.10s). Beautiful day, car went strong at 40 mph for most of the ride. Temp held steady at 190 for most of the trip (except stop lights). Only issue was an occasional hesitation when accelerating from a stop, and some brief bursts of white smoke from the exhaust when that hesitation occurred. I need to figure out what is causing that.

Can't wait for the new gears in the back!
 

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64-67 Expert
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4.10s will cause a car to run hot at speed, as you found out. No need for them on a Pontiac, unless you are drag racing with some large diameter slicks. Even then, not much good. New gears will change the car. Hopefully you're going 3.36 or lazier.....(I stuffed a 2.56 in my '67, but it's an automatic) Congrats on your progress!
 

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Discussion Starter #3
Nope, no dragging my future. I'm thinking I will drop to 3.31. The car has a non-original GM 12-bolt. That 3.31 gets me pretty close to the 3.36 it came from the factory with. Slowly but surely I'm getting it back closer to stock.

Down the line I'd like to pull the Street Dominator intake and Edlebrock carb and get a stock 4 barrel intake and Q-jet as well.
 

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64-67 Expert
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Yep. Being wound up tight at 65mph is no fun, with the Hyundai's blowing by you.....a 3.31 gearset would be an excellent all-around choice, stick or auto.
 

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Iras 67

I had no clue about any of this when I got our 67 GTO and have since learned it has a 2.92 rear end because it was ordered with air conditioning. I was at first disappointing because I had owned Chevy's that smoked off the line with 4:11 rear ends in the past. I have found through the limited driving I have now done that my past ideas were incorrect. The 2.92 rear end was well thought out by Pontiac engineers. The car scoots off the line like no ones business but more importantly she cruises like a dream. I don't have a tach on it yet but I would be willing to bet my trained ear tells me at 60 she is turning no more than 2k rpm. I stepped into it at 50 and laid off at 90 and she was still not sweating in the least bit. I feel confident she will run all day at 90 without working to hard. It is amazing the car is so smooth at these higher speeds considering she is 46 years old. I feel like they designed this combo to be an every day driver cruiser that would beat most cars of the day off the line and still be perfect for a cross country trip. Why don't they make then like this anymore...its like art.
 

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Discussion Starter #7
Yeah, I really can't wait to see how the new gears feel. I've been waiting on the swap for years, and I think I've missed out on enjoying the car because of it. Long over due.

I'm hoping I can keep this momentum going. I lost steam on the car for the last 5-6 years or so.
 

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I had no clue about any of this when I got our 67 GTO and have since learned it has a 2.92 rear end because it was ordered with air conditioning. I was at first disappointing because I had owned Chevy's that smoked off the line with 4:11 rear ends in the past. I have found through the limited driving I have now done that my past ideas were incorrect. The 2.92 rear end was well thought out by Pontiac engineers. The car scoots off the line like no ones business but more importantly she cruises like a dream. I don't have a tach on it yet but I would be willing to bet my trained ear tells me at 60 she is turning no more than 2k rpm. I stepped into it at 50 and laid off at 90 and she was still not sweating in the least bit. I feel confident she will run all day at 90 without working to hard. It is amazing the car is so smooth at these higher speeds considering she is 46 years old. I feel like they designed this combo to be an every day driver cruiser that would beat most cars of the day off the line and still be perfect for a cross country trip. Why don't they make then like this anymore...its like art.
You are correct sir, pontiacs are made to be driven. These motors make massive torque low in the rev range so they can push a tall gear. I still have the 2:56 in mine and i got 16.5 MPG on a recent 1.5 hr freeway trip and thats with a 473 cubes. Have a chevy 12 bolt posi all prepped and ready to go in with a 3:55 and i think i will just wait until the 10 bolt peg leg gives out.
 

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Ira, you have a 2.93 to one ratio back there. I know, I'm knit-picking. Back in 1980, a buddy of mine had a near mint '67 GTO cameo ivory/gold interior auto car with AC. Bought it from the original owner. It also had the 2.93 rear end...his was a limited slip unit. His car had the rally gauges, so it had a tach. I remember one time on the freeway we were racing a black '65-ish Corvette with a big block in it and 4.11's. At about 100 mph, he was topped out, wound out. My buddy just booted it and we left him like he was standing still. Another time, we were racing a brand new '80 Z-28, and when he was topped out and we were side by side, my buddy stomped on it and it kicked down into passing gear and we were gone. Blew the guy's mind. At 100 mph, we were at 4100 rpm. At 100 mph, my 3.55 geared '66 GTO was near redline. What a difference. I have a 2.56 transplanted into my own '67, and it gets over 20mpg (21 at times) at 75-80 mph. It's doggy off the line compared to the 2.93, but it'll still burn plenty of rubber. I think the IDEAL rear end for an automatic equipped, street driven GTO is a 2.93.
 

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I had no clue about any of this when I got our 67 GTO and have since learned it has a 2.92 rear end because it was ordered with air conditioning. I was at first disappointing because I had owned Chevy's that smoked off the line with 4:11 rear ends in the past. I have found through the limited driving I have now done that my past ideas were incorrect. The 2.92 rear end was well thought out by Pontiac engineers. The car scoots off the line like no ones business but more importantly she cruises like a dream. I don't have a tach on it yet but I would be willing to bet my trained ear tells me at 60 she is turning no more than 2k rpm. I stepped into it at 50 and laid off at 90 and she was still not sweating in the least bit. I feel confident she will run all day at 90 without working to hard. It is amazing the car is so smooth at these higher speeds considering she is 46 years old. I feel like they designed this combo to be an every day driver cruiser that would beat most cars of the day off the line and still be perfect for a cross country trip. Why don't they make then like this anymore...its like art.
I'm running 2.92's in mine as well and you're right... It's cruising along at 90 without a care in the world. I'm running 235-60x15s and 65 mph is something like 2200 RPM's. I can't say for sure because my speedo is off a tad due to the taller tires. All I know, is this thing lives for the open road.
 

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Ira, you have a 2.93 to one ratio back there. I know, I'm knit-picking. Back in 1980, a buddy of mine had a near mint '67 GTO cameo ivory/gold interior auto car with AC. Bought it from the original owner. It also had the 2.93 rear end...his was a limited slip unit. His car had the rally gauges, so it had a tach. I remember one time on the freeway we were racing a black '65-ish Corvette with a big block in it and 4.11's. At about 100 mph, he was topped out, wound out. My buddy just booted it and we left him like he was standing still. Another time, we were racing a brand new '80 Z-28, and when he was topped out and we were side by side, my buddy stomped on it and it kicked down into passing gear and we were gone. Blew the guy's mind. At 100 mph, we were at 4100 rpm. At 100 mph, my 3.55 geared '66 GTO was near redline. What a difference. I have a 2.56 transplanted into my own '67, and it gets over 20mpg (21 at times) at 75-80 mph. It's doggy off the line compared to the 2.93, but it'll still burn plenty of rubber. I think the IDEAL rear end for an automatic equipped, street driven GTO is a 2.93.
You are correct sir, that was what I call a beer typo lol. thanks
 
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