Is 3.27:1 R/E Too High For A 3.27 340HP
#1
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Is 3.27:1 R/E Too High For A 3.27 340HP
I am removing my original 4.11 R/E and replacing it with a more highway friendly rear end. I found a 1963 station wagon Posi 3.27 rear end. Since I have the original 4sp T10 my final gear ratio is 1:1. With this final T10 gear ratio the 3.27 rear end ratio, the RPM at 70mph is about 2800rpm. Not bad, but I was thinking of using a 3.36 or a 3.55.
I am trying to beef up my 327 340hp to about 375hp with a roller cam and roller tip rockers. Great midrange Lunati Cam
I am wondering if anyone is using a 3.27 rear end with a similar engine and transmission? A 3.56?
Bob
I am trying to beef up my 327 340hp to about 375hp with a roller cam and roller tip rockers. Great midrange Lunati Cam
I am wondering if anyone is using a 3.27 rear end with a similar engine and transmission? A 3.56?
Bob
#2
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I am wondering how a '63 wagon got a 3.27 rear gear?
A 3.36 gear with a wide ratio four speed will work fine for normal stop/go driving but you'll think you lost 50 horsepower over the 4.11.
A 3.36 gear with a close ratio transmission isn't too good at all for much stop/go driving.
A 3.36 gear with a wide ratio four speed will work fine for normal stop/go driving but you'll think you lost 50 horsepower over the 4.11.
A 3.36 gear with a close ratio transmission isn't too good at all for much stop/go driving.
#3
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I assume you are talking about a '62 with a solid axle.
Gearing depends on your mix of city/highway driving and the hilliness of your terrain. A CR trans with a tall gear will make starting out somewhat difficult, more sluggish performance off the line, and shorter clutch life.
Consider installing the tall gear along with a transmission swap. A lot of guys use various five speeds, but there are usually significant integration issues. Consider a Richmond Super T-10 with the 2.88. 1.91, 1.33, 1.00:1 ratio set. It should integrate relatively easy. The spline counts may be different, so a different clutch disk and driveshaft yoke might be required, but I believe the OE linkage will bolt right on.
The 2.88 first gear with a 3.27 axle would be equivalent to a 2.20 low CR trans and a 4.28 axle, so about the same as your OE combination. The intergear ratios are 1.51, 1.44, and 1.33. The one-two gap is pretty wide, but won't be than noticeable, and then the ratios become closer as you work your way up. This is the opposite of early T-10 and Muncie wide ratio transmissions that have close 1-2, 2-3 intergear ratios and then a huge gap to fourth.
If you have Excel search for threads stated by me and download the gear chart program and have at it.
Duke
Gearing depends on your mix of city/highway driving and the hilliness of your terrain. A CR trans with a tall gear will make starting out somewhat difficult, more sluggish performance off the line, and shorter clutch life.
Consider installing the tall gear along with a transmission swap. A lot of guys use various five speeds, but there are usually significant integration issues. Consider a Richmond Super T-10 with the 2.88. 1.91, 1.33, 1.00:1 ratio set. It should integrate relatively easy. The spline counts may be different, so a different clutch disk and driveshaft yoke might be required, but I believe the OE linkage will bolt right on.
The 2.88 first gear with a 3.27 axle would be equivalent to a 2.20 low CR trans and a 4.28 axle, so about the same as your OE combination. The intergear ratios are 1.51, 1.44, and 1.33. The one-two gap is pretty wide, but won't be than noticeable, and then the ratios become closer as you work your way up. This is the opposite of early T-10 and Muncie wide ratio transmissions that have close 1-2, 2-3 intergear ratios and then a huge gap to fourth.
If you have Excel search for threads stated by me and download the gear chart program and have at it.
Duke
#4
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Thread Starter
I am assuming the '62 4 speed is a close ratio. Am I correct?
The ring gear had 36 teeth, the pinion had 11 teeth. It's a Posi.
Bob
The ring gear had 36 teeth, the pinion had 11 teeth. It's a Posi.
Bob
Last edited by 6T2Vette; 12-15-2018 at 11:19 AM.
#5
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Thread Starter
I assume you are talking about a '62 with a solid axle.
Gearing depends on your mix of city/highway driving and the hilliness of your terrain. A CR trans with a tall gear will make starting out somewhat difficult, more sluggish performance off the line, and shorter clutch life.
Consider installing the tall gear along with a transmission swap. A lot of guys use various five speeds, but there are usually significant integration issues. Consider a Richmond Super T-10 with the 2.88. 1.91, 1.33, 1.00:1 ratio set. It should integrate relatively easy. The spline counts may be different, so a different clutch disk and driveshaft yoke might be required, but I believe the OE linkage will bolt right on.
The 2.88 first gear with a 3.27 axle would be equivalent to a 2.20 low CR trans and a 4.28 axle, so about the same as your OE combination. The intergear ratios are 1.51, 1.44, and 1.33. The one-two gap is pretty wide, but won't be than noticeable, and then the ratios become closer as you work your way up. This is the opposite of early T-10 and Muncie wide ratio transmissions that have close 1-2, 2-3 intergear ratios and then a huge gap to fourth.
If you have Excel search for threads stated by me and download the gear chart program and have at it.
Duke
Gearing depends on your mix of city/highway driving and the hilliness of your terrain. A CR trans with a tall gear will make starting out somewhat difficult, more sluggish performance off the line, and shorter clutch life.
Consider installing the tall gear along with a transmission swap. A lot of guys use various five speeds, but there are usually significant integration issues. Consider a Richmond Super T-10 with the 2.88. 1.91, 1.33, 1.00:1 ratio set. It should integrate relatively easy. The spline counts may be different, so a different clutch disk and driveshaft yoke might be required, but I believe the OE linkage will bolt right on.
The 2.88 first gear with a 3.27 axle would be equivalent to a 2.20 low CR trans and a 4.28 axle, so about the same as your OE combination. The intergear ratios are 1.51, 1.44, and 1.33. The one-two gap is pretty wide, but won't be than noticeable, and then the ratios become closer as you work your way up. This is the opposite of early T-10 and Muncie wide ratio transmissions that have close 1-2, 2-3 intergear ratios and then a huge gap to fourth.
If you have Excel search for threads stated by me and download the gear chart program and have at it.
Duke
I have a '56 BelAir 2dr HT with a 327 with about 300horse. I installed a 3.36 Posi unit in it. I am using the OE 3 on the tree with overdrive. What a sweetheart to drive. Just like driving a 5 speed. I can cruise at 70mph doing about 2300rpm.
With 3.56 gears I imagine I'll be spinning about 3 grand at the same speed?
Bob
#6
the GM archive center shows the 62 with a 340 received the close ratio box with a 3.70 rear. it shows optional rears as low as 3.08. What does Lunati say is the appropriate ratio for their cam?
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
#7
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Thread Starter
the GM archive center shows the 62 with a 340 received the close ratio box with a 3.70 rear. it shows optional rears as low as 3.08. What does Lunati say is the appropriate ratio for their cam?
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
Perhaps someone can enlighten me, The Lunati Voodoo roller cam number is #201207 with roller tip rockers.
Bob
#8
Melting Slicks
If it were mine, I would install a 3.55 rear end with your 2.20 4 speed if you want easier highway miles. Maybe even a 3.70.
And I wouldn't install roller rocker arms. Or a roller cam. But it's your car.
And I wouldn't install roller rocker arms. Or a roller cam. But it's your car.
#9
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What you propose makes zero sense. More performance with less axle ratio. You'll never get it to move from dead stop without slipping the **** out of the clutch. detune the engine to 300 hp spec or put in a 5speed overdrive or forget it.
#10
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Duke, I'm already swapping the rear end on a numbers correct car. I wanted to stop there so I want to use the OE 4sp. I assumed all '62's had solid axles.
I have a '56 BelAir 2dr HT with a 327 with about 300horse. I installed a 3.36 Posi unit in it. I am using the OE 3 on the tree with overdrive. What a sweetheart to drive. Just like driving a 5 speed. I can cruise at 70mph doing about 2300rpm.
With 3.56 gears I imagine I'll be spinning about 3 grand at the same speed?
Bob
I have a '56 BelAir 2dr HT with a 327 with about 300horse. I installed a 3.36 Posi unit in it. I am using the OE 3 on the tree with overdrive. What a sweetheart to drive. Just like driving a 5 speed. I can cruise at 70mph doing about 2300rpm.
With 3.56 gears I imagine I'll be spinning about 3 grand at the same speed?
Bob
First gear in the CR T-10 with a 3.70 is very close to the 3-speed with a 3.36. GM did not fit a 3.36 with the CR T-10 in 1962, so it is unlikely that someone has the exact combination to offer advice.
Second gear in the CR T-10 with a 3.36 is very close to second gear with the 3-speed with a 3.36 (one you get out of first gear the performance through gears 2, 3, & 4 will be better than with your 56' BelAir).
The model of your cam selection in earlier threads indicate engine performance similar to the GM 350hp hydraulic cam, with an expected improvement in low rpm torque over the GM cam due to the roller lifter cam profile (making low rpm launches less trouble). Maybe someone with a CR Muncie and a 3.36 in a later 350hp/327 can offer what they experience (the closest real world comparison)?
Nobody but you can make the comfort call you are asking opinions about (use your 56' experience as your guide).
#11
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Thread Starter
In essence, what I'm doing is dropping my compression ratio, adding an excellent mid range cam, improving air flow from my camel back heads with 2.5" exhaust, keeping my original T10 4sp, and replacing my original 4.11 Posi with a 3.55 Posi. I have no idea where my HP will wind up at, but the machinist sez it will be better than the original 340...
Still make zero sense, please tell me where I'm wrong so I can stop payment on the last check I gave my machinist.
Bob
#12
Race Director
I would go with a 3:55 and 5 speed with .6 overdrive - great on the highway and great around town.
I have a vette with 3:36 + stock auto and it's not bad as an all around setup.
I also have a 3:55 and 5 speed vette - much more fun....
I have a vette with 3:36 + stock auto and it's not bad as an all around setup.
I also have a 3:55 and 5 speed vette - much more fun....
#13
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Thread Starter
If you don't mind the clutch slip needed to launch your much heavier 56' BelAir, with the 3.36 rear gear, the lighter Corvette should not be a bigger problem.
First gear in the CR T-10 with a 3.70 is very close to the 3-speed with a 3.36. GM did not fit a 3.36 with the CR T-10 in 1962, so it is unlikely that someone has the exact combination to offer advice.
Second gear in the CR T-10 with a 3.36 is very close to second gear with the 3-speed with a 3.36 (one you get out of first gear the performance through gears 2, 3, & 4 will be better than with your 56' BelAir).
The model of your cam selection in earlier threads indicate engine performance similar to the GM 350hp hydraulic cam, with an expected improvement in low rpm torque over the GM cam due to the roller lifter cam profile (making low rpm launches less trouble). Maybe someone with a CR Muncie and a 3.36 in a later 350hp/327 can offer what they experience (the closest real world comparison)?
Nobody but you can make the comfort call you are asking opinions about (use your 56' experience as your guide).
First gear in the CR T-10 with a 3.70 is very close to the 3-speed with a 3.36. GM did not fit a 3.36 with the CR T-10 in 1962, so it is unlikely that someone has the exact combination to offer advice.
Second gear in the CR T-10 with a 3.36 is very close to second gear with the 3-speed with a 3.36 (one you get out of first gear the performance through gears 2, 3, & 4 will be better than with your 56' BelAir).
The model of your cam selection in earlier threads indicate engine performance similar to the GM 350hp hydraulic cam, with an expected improvement in low rpm torque over the GM cam due to the roller lifter cam profile (making low rpm launches less trouble). Maybe someone with a CR Muncie and a 3.36 in a later 350hp/327 can offer what they experience (the closest real world comparison)?
Nobody but you can make the comfort call you are asking opinions about (use your 56' experience as your guide).
Bob
#15
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Keep in mind, your '56 Bel Air transmission has a 2.94 1st gear ratio which makes a whole lot difference vs the 2.20 first gear in your Borg Warner in the overall gear ratio.
One of the posters here has often said he bought a new 340 hp Sting.Ray/StingRay with the close ration transmission and the 3.08 axle. Ask him how he liked it for everyday stop/go driving.
Do a search on threads started by me to get accurate answers to your gears.
Last edited by MikeM; 12-15-2018 at 06:45 PM.
#16
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#17
Melting Slicks
I would get at least one or two more opinions from different shops on this build.
I also wouldn't drop the compression ratio to 9-1. That will kill any possible horsepower that the new fancy cam may add.
And hopefully, he won't recommend going to larger (1.6"-2.02") valves. That's another instant death.
Take your time and do some research on this.
There are a lot of very knowledgeable people here. (not me....... I'm just a dope that stops in here sometimes)
Last edited by Critter1; 12-15-2018 at 07:08 PM.
#18
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Thread Starter
Keep in mind, your '56 Bel Air transmission has a 2.94 1st gear ratio which makes a whole lot difference vs the 2.20 first gear in your Borg Warner in the overall gear ratio.
One of the posters here has often said he bought a new 340 hp Sting.Ray/StingRay with the close ration transmission and the 3.08 axle. Ask him how he liked it for everyday stop/go driving.
Do a search on threads started by me to get accurate answers to your gears.
One of the posters here has often said he bought a new 340 hp Sting.Ray/StingRay with the close ration transmission and the 3.08 axle. Ask him how he liked it for everyday stop/go driving.
Do a search on threads started by me to get accurate answers to your gears.
Bob
#19
Are you going with a carb or injection? In my opinion you need to STOP! Come up with a game plan first. Light weight car, less torque is needed. How are going drive it, how far, how much... Then exacute a solid plan.
#20
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Thanks for your voted of confidence. Please keep in mind I have an overdrive 3sp in the '56 with the 327. That means that with the Borgward overdrive I have two different speeds for every gear shift...including 1st, which is near impossible. So in reality I have 5 speeds out of a 3 speed with my final OD ratio at 1 to .070.
Bob
Bob
If you want the same 2.94 first gear grunt of your 56' BelAir 3-speed, and the .070 high gear cruise rpm of the 3-speed with the OD, then you should be looking at wide ratio 5-speed or 6-speed transmissions.
Keep in mind, any transmission without a wide range like the BelAir combination will be a compromise, either on a start from dead stopped, or with the cruise rpm (pick you favored benefit, and decide).
Keep in mind, that every bit of free advice is worth what you are paying others to ignore it (your choice of words and phrases, and final decisions, come off reading a bit unappreciative).