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Discussion Starter #1
Planning on buying a 67 Cougar. Engine and Transmission are sound. I need to drive it home (100 miles) most at highway speeds of 55-65. During the test drive, engine seemed to RPM high at these speeds. Person I'm buying it from said it's from the rear differential gear ratio. I believe this might be the case. Will I do any damage driving the car that distance and that speed with the gear ratio where it is and the engine running at a high RPM? It's a 3 speed automatic transmission by the way on a 289. Can it be changed or would you advise changing. THANKS
 

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Discussion Starter #3
Don't have that information, but I don't think it was unusually high, just not what you get with modern day cars. All I know is it seemed to be running high and I looked down to see if was in a low gear. I had my son with me and he noticed this as well as did the seller. That's when he made the gear ratio comment but he didn't know what it was set at. My son noticed it too, but said it was normal, and agreed it was the gear ratio. I've read different threads that state this is normal with a 3 speed automatic. Will I damage the engine running at that speed for that distance.
 

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A three speed, or a four speed for that matter, are a 1:1 ratio in high gear. All newer cars have an over drive gear, allowing for lower cruising RPM's.
If the seller knows what the rear end gear ratio is, (other that stock?) Find out what it is. A 3.25 or a 3.50, should be no problem cruising 60 MPH. If it is a taller gear, I.E., 3.89 or 4.11, then you may want to think about a trailer. Is it a stock engine, or built up with a gnarly cam?
Provided that it isn't a built motor, just make sure it is in "D" and you should be fine...
 

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Discussion Starter #5
It's a stock rebuilt engine but no modifications. Not knowing anything about gears I can't imagine the stock gears were swapped for the taller ones. Question: to go from a 3.25 or 3.50 to a 3.89 or 4.11 does the gear have to be swapped out or is it a setting?
 

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Discussion Starter #7
Thanks Cedar Rapids Ia, good to know in case I need to swap them back. Which I don't think is the case with this. I think I'm just used to newer cars that have overdrive at high speeds.
 

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If it's a 9" rear, you could look for another carrier assembly with the ratio you want set up and ready to go, but I would try to ID what you have first. You can decode the tag information or look to see if the ID tag is still on the bolt of the rearend (and legible)....or another option would b to upgrade to an overdrive trans....but not a cheap option.
 

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Thanks Cedar Rapids Ia, good to know in case I need to swap them back. Which I don't think is the case with this. I think I'm just used to newer cars that have overdrive at high speeds.
There's your answer right there.

When I started to ride motorcycles it took a long time to get used to the higher revs at a given speed. I would keep trying to upshift when I was already in the highest gear.

It takes a few minutes to get used to the higher engine speed when I get behind the wheel of my Cougar. A friend has a 69 Cougar with a 5-speed manual trans and the overdrive makes a big difference at freeway speeds.

You should be OK. Just monitor the engine's vitals (temperature and oil pressure).
 

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FYI taller gears are lower numbers. Deeper or shorter gears are higher numbers. AKA 2.75 = tall, 4.10 deep/ short.
BTW my 67 standard turns just under 2400 RPM at 60 MPH with 3.00 gears. 215/70-14 tires.

Bill
 

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It may well just be a sound sensation from the dual exhaust. I think you posted somewhere that it had a good sounding dual? Anyway the sensation of speed is enhanced by sound like when some guys swap out the mufflers on their bikes and claim they can feel how much faster it is. In reality one would need a stop watch to really see any diff whereas the increase in power is so miniscule. I drove my Mach with a 4.56 at 60 mph all the time. Just had to feed it that Sunoco 260! Watch the temp too.
 

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Discussion Starter #13
Got my 67 Cougar today. Does have a 3.89. Drove it 100 miles to get it home. 55-60 MPH. Ran great. And I think your right, letsroll, the exhaust does seem to exagerate the actual RPM of the engine.
 

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Got my 67 Cougar today. Does have a 3.89. Drove it 100 miles to get it home. 55-60 MPH. Ran great. And I think your right, letsroll, the exhaust does seem to exagerate the actual RPM of the engine.
3.89 is pretty stout behind a stock engine with an automatic. Make it jump off the line well but gonna be friendly at the gas stations! Keep us posted on the new prize!
 
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