1970 SS 12 BOLT gear ratio's? - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 9 (permalink) Old Jul 11th, 08, 11:28 PM Thread Starter
Anthony
 
Join Date: Apr 2008
Location: Omaha
Posts: 6
1970 SS 12 BOLT gear ratio's?

I thought it to would be easy to find information on what gear ratios came in a stock 12 bolt under a 1970 SS Chevelle or El Camino, but I guess I was wrong.

Can anyone help me out? Is there a chart that shows all the factory options?

Also,

What gears would be good for a cruiser with a 400 SBC and 4spd Muncie?
79scout-too is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old Jul 11th, 08, 11:41 PM
Senior Tech Team
Andrew
 
Join Date: Apr 2001
Location: The Druid City
Posts: 1,896
Re: 1970 SS 12 BOLT gear ratio's?

Quote:
Originally Posted by 79scout-too View Post
I thought it to would be easy to find information on what gear ratios came in a stock 12 bolt under a 1970 SS Chevelle or El Camino, but I guess I was wrong.

Can anyone help me out? Is there a chart that shows all the factory options?

Also,

What gears would be good for a cruiser with a 400 SBC and 4spd Muncie?
How much highway driving are you going to do? How tall are your tires?

Andrew

1970 GTO Version 2.0 in progress
V8TV Feature video
Popular Hotrodding feature
Car Craft feature
1967 Cougar LSx build

"You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets."
andrewb70 is offline  
post #3 of 9 (permalink) Old Jul 12th, 08, 8:34 AM
Team Member
 
Join Date: Jun 2002
Location: N.Y.
Posts: 11,147
Smile Re: 1970 SS 12 BOLT gear ratio's?

331 to 342 max for all arround comprimise between decent performance when getting into it and reasonable cruise rpm with a non o/d trans,maybe even 308 if your not into the peformance end that much.

But gear like 355/373/410 etc gear is too much for reasonable street duty these days $5 gal fuel without an o/d trans and or very tall tires IMHO.

Depends on what you want,not what we prefer becausee some people think 373 gear with non o/d trans is fine on the road with 26" tires turning APPROX 3k rpms @ 60mph which can get old quickly depending on setup/how loud it is. If thats you go for 373 ,but if not go for the 342 331/331 is only avail used or nos on ebay or local swap meets but there is talk ofthe 331's being mfg's again but not yet from what i understand.

Scott

SCOTT
1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
2009 HD ELECTRAGLIDE CLASSIC ULTRA (GOT 11/14 W-9,700 miles)

Last edited by SWHEATON; Jul 12th, 08 at 12:05 PM.
SWHEATON is offline  
post #4 of 9 (permalink) Old Jul 12th, 08, 10:45 AM
Senior Tech Team
Jon
 
Join Date: Jan 2005
Location: irving,texas
Posts: 1,073
Send a message via Yahoo to 70 beater
Re: 1970 SS 12 BOLT gear ratio's?

If you can find an unmolested rear there may be a tag on it with the ratio.May want to try the tag team or restoration corner forum.The 12 bolt I've got had 2.73 factory gears,non SS,it has 4.56 now. I'm thinking that the 4.11:1 gears were common for the SS cars,might depend some on if the car was manual or auto,or maybe the had to be checked off,I've got a book,somewhere,maybe it will say something.

Jon
North Texas Chevelles
70 Chevelle Melba Rust
glorified parts car
7.86 @91(1/8 w/sbc)
JAKESHOE TH 400
70 beater is offline  
post #5 of 9 (permalink) Old Jul 12th, 08, 11:01 AM
Senior Tech Team
 
Join Date: Jul 1999
Location: Talking Rock, Ga
Posts: 1,358
Re: 1970 SS 12 BOLT gear ratio's?

Stock ratio was a 3.31, with posi as an option. There were a few 3.55 gears in early cars, (pre-December), and also an option for a 4.10 ratio. That was it for '70.
Doug Garland is offline  
post #6 of 9 (permalink) Old Jul 12th, 08, 11:24 PM Thread Starter
Anthony
 
Join Date: Apr 2008
Location: Omaha
Posts: 6
Re: 1970 SS 12 BOLT gear ratio's?

Thanks guys. I think I will be lifting my el camino some and running 28"-30ish" tires. Not sure as of now just curious about what gears to look for as I search for a 12 bolt to swap in.
79scout-too is offline  
post #7 of 9 (permalink) Old Jul 13th, 08, 8:07 PM
Tech Team
larry
 
Join Date: Feb 2007
Location: michigan
Posts: 249
Re: 1970 SS 12 BOLT gear ratio's?

my 12 bolt i sold had a 3:08 rear
greasemonkey427 is offline  
post #8 of 9 (permalink) Old Jul 14th, 08, 8:12 AM
Senior Tech Team
Tom
 
Join Date: Sep 1998
Location: Mustang, OK USA
Posts: 11,357
Re: 1970 SS 12 BOLT gear ratio's?

The 12bolt in the 70 conv is a 3.07 posi (they were 3.08 in a 10 bolt).
I have a healthy SB400 and a wide ratio Muncie (M20) also, and the combo is just right for cruisin' and Interstate driving. Admittedly, from a dead stop, it does not leave like a rocket. But the SB400 has plenty of torque to make the M20/3.07 combo work just fine.
And with today's gas prices, I'm not interested dropping to a lower gear ratio.

Tom Parsons
TC# 474
#3 FOREVER!!!!!
Light travels faster than sound. That is why some people appear to be bright until you hear them speak. (unknown)
DZAUTO is offline  
post #9 of 9 (permalink) Old Jul 14th, 08, 12:19 PM
Team Member
 
Join Date: Jun 2002
Location: N.Y.
Posts: 11,147
Smile Re: 1970 SS 12 BOLT gear ratio's?

Yeh Tom,i went from the stock 307's in my 12 bolt to 331s approx 5-4 yrs ago in my 69 chevelle with mild 396(approx370hp/440lbs trq) & m20 and the perf inc was decent even with small gear change.

But since fuel prices have gone nuts and i am finding myslef doing more open road/interstate crusing to new shows/cruises i am really considering re-installing the original 307's in the near future.
scott

SCOTT
1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
2009 HD ELECTRAGLIDE CLASSIC ULTRA (GOT 11/14 W-9,700 miles)
SWHEATON is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome