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Discussion Starter · #1 ·
I have a stock 55 Chevy with a 235 6-cyl one barrel carb that I just installed a non OD 3 speed manual transmission. What diff. ratio should I use? A 3.08 or 3.36 and why?

Been told that the 6 cylinder just doesn't have enough torque to get it moving with a 3.08, but once it does everything's okay. Obviously the 3.36 would help from a complete stop, but how much will this affect 6-cyl rpms on the highways?

I live out in the country and 80%+ of my driving is highway.

Would like to hear from somebody who has actual experience with this.

Thank you in advance.
 

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First gear in that trans is pretty low so taking off shouldn’t be an issue with either of those ratios. Personally I’d use the 3.36 if that’s what you have. It would be ok with the 3.08 as well. You can always swap either out if you don’t like it. There’s plenty of these gears laying around yet.
 

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Discussion Starter · #3 ·
First gear in that trans is pretty low so taking off shouldn’t be an issue with either of those ratios. Personally I’d use the 3.36 if that’s what you have. It would be ok with the 3.08 as well. You can always swap either out if you don’t like it. There’s plenty of these gears laying around yet.
Thank you for your input on this. I currently have a 4.11 diff. and as you can imagine, the engine is literally screaming @ 55 mph.
 

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I'd do the 3:08. I have that gear in my 66 Chevelle with a 4 speed, and I'm doing about 2600 rpm at 75/80. That's enough for me. That's why I like the 700R4 I put in my 56, I can go the same speed at about 2100 with a 3:42 gear.
 

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Discussion Starter · #5 ·
I'd do the 3:08. I have that gear in my 66 Chevelle with a 4 speed, and I'm doing about 2600 rpm at 75/80. That's enough for me. That's why I like the 700R4 I put in my 56, I can go the same speed at about 2100 with a 3:42 gear.
I'm kinda leaning that way myself, but looking for more responses. I'm going to try to figure out my 1st and 2nd gear ratios later today. Thank you for your input.
 

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The stock first gear ratio is like 2:98 or 2:94 or something in that range. Non OD 55-56 chevys received 3:73 rears from the factory. So the effective first gear on a non OD stick car is like 11:1. OD cars got 4:11 so more like 12.2 effective first gear. 57s got 3:55s so a little less at 10.5:1. I drove my 6 car all over creation from 77 through 83 as my daily driver. Generally around 60-62 mph or so on the turn pike and highways with 3;55s never a problem.

3:08 is not a good gear set in my opinion. I am not even sure 3:23s are any good. You will have to slip the clutch in order to get the car moving and not lug the motor. Lugging the motor on an early style 235 6 is stressful on the crank, really stressful. These 6 motors are rated at 140 gross HP but that number was optimal. Figure a lot less on a production motor, and figure a lot less, probably less then 100 HP at the rear wheels. You need gear multiplication to get the car moving with a 6 motor which is why the factory geared them the way they did.

Me, I would try a set of 3:55 gears. Its a good all around set of gears and better then the 4:11s you currently have, better for highway type driving.

Keep in mind, that the above reflects the 6 motor. More powerful motors can overcome the low power of the 235 and use the numerically lower gear sets. Same with the later style 6 motors (230, 250, 292). They all make more power then the 235 does and thus can utilize some different gearing.
 

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Discussion Starter · #7 ·
The stock first gear ratio is like 2:98 or 2:94 or something in that range. Non OD 55-56 chevys received 3:73 rears from the factory. So your effective first gear is like 11:1. OD cars got 4:11. 57s got 3:55s so a little less at 10.5:1. I drove my 6 car all over creation from 77 through 83 as my daily driver. Generally around 60-62 mph or so on the turn pike and highways with 3;55s never a problem.

3:08 is not a good gear set in my opinion. I am not even sure 3:23s are any good. You will have to slip the clutch in order to get the car moving and not lug the motor. Lugging the motor on an early style 235 6 is stressful on the crank, really stressful. These 6 motors are rated at 140 gross HP but that number was optimal. Figure a lot less on a production motor, and figure a lot less, probably less then 100 HP at the rear wheels. You need gear multiplication to get the car moving with a 6 motor which is why the factory geared them the way they did.

Me, I would try a set of 3:55 gears. Its a good all around set of gears and better then the 4:11s you currently have, better for highway type driving.

Keep in mind, that the above reflects the 6 motor. More powerful motors can overcome the low power of the 235 and use the numerically lower gear sets. Same with the later style 6 motors (230, 250, 292). They all make more power then the 235 does and thus can utilize some different gearing.
Thank you for your response.
My transmission has a 2.84 1st gear ratio and a 1.68 2nd gear ratio. I really only want to do this one time, so I'm trying my best to get all information available in my decision making process. Definitely don't want to slip the clutch or lug the motor. I'll have a 4.11 that I will no longer need.
 

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Even worse then. 3:08 x 2.84 is an effective first gear of 8.74. That will be pretty tough on the 6 motor and clutch. What kind of trans is that? A later model fully synchronized Saginaw?
 

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Buddy if you are using the trans I sold you it came out of a 57 convertible with 3.55 gears & a crate low performace 350 cruised on the highway just fine someone else stated 6 cylinders manuals used 3.70 gears I think you will end up slipping the clutch going 3.08 maybe 3.36 I love 3.55 personally great all around gear just my opinion
 
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