3.55 gears with four speed - Pontiac GTO Forum
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post #1 of 17 (permalink) Old 08-26-2018, 06:50 PM Thread Starter
 
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3.55 gears with four speed

Looking for opinion on 3.55 gears in a 68 GTO with a four speed manual. Is that going to be a good all around gear for a daily driver? I understand the 3.55 gears were the norm for cars with the four speed, but of course 50 years ago, gas was cheap. I would like to have lower rpms at highway speed, less heat, less noise, better gas mileage. Are the 3.55 gears going to be a decent ratio?? Thanks in advance for your input!
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post #2 of 17 (permalink) Old 08-26-2018, 07:04 PM
 
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Originally Posted by jayvee53 View Post
Looking for opinion on 3.55 gears in a 68 GTO with a four speed manual. Is that going to be a good all around gear for a daily driver? I understand the 3.55 gears were the norm for cars with the four speed, but of course 50 years ago, gas was cheap. I would like to have lower rpms at highway speed, less heat, less noise, better gas mileage. Are the 3.55 gears going to be a decent ratio?? Thanks in advance for your input!
I have the Muncie 4 speed and 3.55 rear in my 65. I think the rear is fine for around town, but if you are planning on a lot of highway driving, you may want to consider a taller gear IMHO.

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #3 of 17 (permalink) Old 08-26-2018, 08:34 PM
 
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Originally Posted by jayvee53 View Post
Looking for opinion on 3.55 gears in a 68 GTO with a four speed manual. Is that going to be a good all around gear for a daily driver? I understand the 3.55 gears were the norm for cars with the four speed, but of course 50 years ago, gas was cheap. I would like to have lower rpms at highway speed, less heat, less noise, better gas mileage. Are the 3.55 gears going to be a decent ratio?? Thanks in advance for your input!
What type transmission? M20, M21 M22?

If you use one of the online calculators you can determine your engine's RPM at whatever speeds you want to run.

The 3.55's were a good gear when the national speed limits were 55MPH. Not so good if you plan on running 70MPH.

As you drop below 3.55's you want to take into consideration that it may use a little more clutch technique in slipping the clutch to get rolling. 3.23's are about as low as you really want to go, but you can run a 3.08 with the low first gear.

The only real way to have your cake and eat it to is to use an overdrive transmission.
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post #4 of 17 (permalink) Old 08-26-2018, 09:26 PM Thread Starter
 
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What type transmission? M20, M21 M22?

If you use one of the online calculators you can determine your engine's RPM at whatever speeds you want to run.

The 3.55's were a good gear when the national speed limits were 55MPH. Not so good if you plan on running 70MPH.

As you drop below 3.55's you want to take into consideration that it may use a little more clutch technique in slipping the clutch to get rolling. 3.23's are about as low as you really want to go, but you can run a 3.08 with the low first gear.

The only real way to have your cake and eat it to is to use an overdrive transmission.
Thanks PontiacJim! The info you sent in regard to my other post seems to be answer to what I am looking for!
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post #5 of 17 (permalink) Old 08-27-2018, 10:00 AM
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Yeah, I've got 3.50's in my 69 (Moser 9-inch) with a TH400. They're a little much for highway at 70mph.

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post #6 of 17 (permalink) Old 08-28-2018, 12:35 PM Thread Starter
 
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Thank you Bear. I am looking for a car comfortable to drive anywhere.....no interest in burning up $200 tires, etc. Maybe I should be considering a non-four speed....
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post #7 of 17 (permalink) Old 08-28-2018, 01:11 PM
 
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Thank you Bear. I am looking for a car comfortable to drive anywhere.....no interest in burning up $200 tires, etc. Maybe I should be considering a non-four speed....
Hmmm, maybe you should consider a new Cadillac....Just saying.....
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1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #8 of 17 (permalink) Old 08-28-2018, 03:06 PM Thread Starter
 
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Hmmm, maybe you should consider a new Cadillac....Just saying.....


As Larry the Cable Guy would say:

"Now that's funny! I don't care who you are!" Well said cij911!

John
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post #9 of 17 (permalink) Old 09-02-2018, 05:20 PM
 
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I ran 3.55 gears in my 4 speed '67 GTO. I thought it was a great gear, but couldn't leave it alone. I went to 3.73 gears. Big mistake. Engine worked harder. More gas. Tough on the interstates which I tried to avoid. I'm presently running 3.55 gears in my '71 GTO with a TH400 trans. They work very well for my driving habits. I wouldn't want any gear numerically higher without an OD transmission. That's just me.
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post #10 of 17 (permalink) Old 09-02-2018, 11:04 PM
 
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I have a 3.55/4 speed '69 convertible. Works great for local cruising.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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