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Steve70Carlo

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Hey Guys,

 

I've had my 70 FOR 16 years. Currently I am running a .030 over 454 with a mild cam, a full manual valve body 400 Turbo trans with a 3200 stall and 4.10 posi.

 

Its been that way for about 10 years and I want to have a more street-friendly car.

 

Two questions:

 

A.) Can't I just switch out the converter for something like a 2200 stall or less without having the entire trans redone?

 

B.) What kind of gears would work with the 12 bolt I have? I see a bunch of different options on web sites and am not sure what to get. I would like to go with a 2.73 or 3.08.

 

This is just a shot in the dark, but if anyone would have these parts (converter or gears), I would be interested in buying those.

 

Thanks for any help!

 

Steve

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Depending on how efficient you torque converter is it may be ok. The biggest issue is that you carrier is a 4 series 3.90 and up gears. Depending on your gear choice you will need a 2 or 3 series. That makes the cost go up on the gear change.

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Thanks Guys,

 

 

Mike- So if I were to look at a 3.08 gear ratio, which series would I need? I'm mechanically inclined but have never changed gears before. Is this something that I could do myself?

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Here is some info from the Mark Williams site

 

CARRIER CONFUSION: When shopping for 12-bolt differential parts, keep this in mind: Chevrolet generally used three different types of differentials for the 12-bolt -- the two series carrier, the three series carrier and the four series carrier. The "two series" has little use in a hi-po application and should be avoided if at all possible. The three series carrier accepted ring and pinions that ranged from 3.08:1 to 3.73:1 while the four series carrier accepted ring and pinions ranging from 3.90:1 to 6.14:1. While there are a number of subtle variations between the three types of carriers, a major difference is the thickness of the gear flange. Two series carriers are the thinnest while three series flanges are thinner than four series flanges. Because of the size of the flange, the carriers cannot be randomly used with ring and pinion sets from the trio of "families".

 

I think that there is a write up on gear swaps, try the search function.

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Here is some info from the Mark Williams site

 

CARRIER CONFUSION: When shopping for 12-bolt differential parts, keep this in mind: Chevrolet generally used three different types of differentials for the 12-bolt -- the two series carrier, the three series carrier and the four series carrier. The "two series" has little use in a hi-po application and should be avoided if at all possible. The three series carrier accepted ring and pinions that ranged from 3.08:1 to 3.73:1 while the four series carrier accepted ring and pinions ranging from 3.90:1 to 6.14:1. While there are a number of subtle variations between the three types of carriers, a major difference is the thickness of the gear flange. Two series carriers are the thinnest while three series flanges are thinner than four series flanges. Because of the size of the flange, the carriers cannot be randomly used with ring and pinion sets from the trio of "families".

 

I think that there is a write up on gear swaps, try the search function.

 

Keep in mind, you can get an Eaton 3 series carrier and install Richmond 4.10/4.11 gears that are built for the 3 series carrier(much thicker ring gear). This ring gear set is actually considered better than the normal 4.10/4,11 gears used for a 4 series carrier. - Dave

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Thanks for all the input so far guys. I'm finding that this could get pretty costly. I built the car about ten years ago and my tastes have changed since then. Back then, I wanted a race car in street clothes, and now I'm looking for more of a cruiser. I removed all heat and ac components, changed the steering to manual steering and installed a super loud exhaust. Just trying to decide which would be a better option at this point. I definitely don't have the cash to do a total revamp of the car.

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If that was my ride, I would go with a 3:31 gear- but changing gears in a 12 bolt is not easy at all. Even if you have all of the specialty tools, getting them "right" is not a straightforward thing. I'd find a mechanic you trust that has done it a few hundred times.

 

Quieting the exhaust is easy and relatively cheap, but the absolute first thing I would do is get rid of the manual valve body. (I've never understood a manual vb- it isn't "reverse" is it? Why shift if you don't have to? You can always shift an automatic if you really want to.)

 

Do those things and then see how if the converter is too annoying. B&M's 2400 is inexpensive and they work very well.

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On the subject of quieting the car down a bit, which mufflers do you guys think I should look at? I heard that Magnaflow has nice mufflers, but there are so many different series that I'm not sure which would work.

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I have the same Magnaflow except in 2.5 inlet/outlet the sound mellow at idle or driving sane but really bellow when you get on it (at a track of course never on the street ;D). They will sound really quiet when you first get them but will break in and get louder after about 6 months of normal driving. David

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What do you guys think about just going with an open rear? I really like having a posi but the way I think about it, is that I'm not racing anymore. Just throwing out some ideas.

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You can still have posi with 2 series gears, ie 2.73 0r 2.56. I have a GM series 2 posi carrier that is shelfed. - Dave

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