How low are 355 gears

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Richie

Richie

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Hi everybody.

I'm wondering what gear set to buy, 323s or 355s They would be matched up to a 904 with a 340. I want to go 60 mph without screaming down the hyw but it would be nice to really get up to 60 mph fast. How many rpms would my motor be turning over with 355s at 60 mph? 2500-3000?
 
Richie said:
Hi everybody.

I'm wondering what gear set to buy, 323s or 355s They would be matched up to a 904 with a 340. I want to go 60 mph without screaming down the hyw but it would be nice to really get up to 60 mph fast. How many rpms would my motor be turning over with 355s at 60 mph? 2500-3000?
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Tire size and converter stall will be in the equation also.
 
14 inch tires. The transmission is stock is all I can tell you about that part. I haven't had anything done to it yet just rebuilt.
 
3.23s would probably be just right.
 
You'll need to know your tire size in inches or at least the width and profile. Like 24.5 inches tall or 195/70/14 for example.

You trans will have a 1.0 high gear so that will give you a 3.23 or 3.55 final drive depending on which way you go.

Let's assume you have 195/70/14 tires. Those should be 24.2 inches tall (plus or minus). at 60 mph the 3.23 will give you 2691rpm, the 3.55 will be 2957 rpm.

I just used a questimate for the tire size but the taller tire you go the lower the rpm will be.
 
Richie said:
14 inch tires. The transmission is stock is all I can tell you about that part. I haven't had anything done to it yet just rebuilt.
Click to expand...

... tire height...

you need tire height, rear gear ratio, and converter stall to figure cruise rpm...

you will be no where near that high with 3.23...


im running 3.91's with a 28" tall tire with a 3400 stall and go 65mph @ 3K rpms (and get 20mpg lol)
 
805 you must have a pretty accurate tach. My math on your setup is right where you say it is. :cheers:
 
323s sound like the way to go then. It's a 13 -14 mile drive to where all my friends are. Hopefully I'll be able to keep up to the Honda's.
 
play around with this... http://www.bigblockdart.com/forum/speedtire.php


it all depends what you want from the car. i had 3.55's in my car with a 38" tire for a summer. it was a lot better then the 3.91 gear i took out but still not how i wanted it because i like to get on the highway for a couple hour trip. if its only short blasts on the highway then you'll be fine. if you want to drive multiple hours of the highway i would go 3.23.
 
Yup, it depends on what you want from your car. I used most of my cars as daily drivers and back and forth to work. 15 miles one way with half and half in town and highway but I still ran gears from 3.23 to 4.10's but I didn't run 14" tires either. Didn't know you could still buy them! May as well go with hi-way gears because the 14's won't do much for ya in traction anyways....if you want that 340 to shine, you need to put some tire behind it. They are good for easy high 13's in stock form but 14's most likely won't put the power to the ground.
 
abodyjoe said:
play around with this... http://www.bigblockdart.com/forum/speedtire.php


it all depends what you want from the car. i had 3.55's in my car with a 38" tire for a summer. it was a lot better then the 3.91 gear i took out but still not how i wanted it because i like to get on the highway for a couple hour trip. if its only short blasts on the highway then you'll be fine. if you want to drive multiple hours of the highway i would go 3.23.
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A 38" tire! That thing must've had a helluva stance! JK :-D
 
3.55 would be my choice with a 225-70 tire or equivalent. It's a compromise - there is no right answer.
 
vwmoparguy said:
805 you must have a pretty accurate tach. My math on your setup is right where you say it is. :cheers:
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its crazy cuz going up to vegas it must be up hill cuz it tacked 200rpm higher the whole way and idled 300 rpm higher once there!
 
Well there is a right answer in terms of final drive ratio in high gear with an automatic and 1:1 ain't it unless you have a lockup converter. It would be different if the torque converter wasn't in the equation. Since converters never completely lock up, you'll never acheive 1:1 in high gear because the converter is a fluid coupling and always has a percentage of slippage. Even more reason to try to keep RPM to a minumum if the car will be commuted a good distance one way.
 
^^^^^^^ How true. My math is just an estimate since I wouldn't know how to estimate torque converter slippage. I deal with standard transmissions and rearends daily. So my formula works well. Automatics are completely foreign to me. But the formula (which is all over the net) will give a baseline for comparisons.
 
I turn about 3000 rpm with a 3:55 rear at 60 mph. My tire is around 26-27" tall I think.
 
not low enough for me.3500 at 60 is what i want with 26 inch tire so 410 or391s
 
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