The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1960 - 1966 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 01-24-2013, 11:58 PM   #1
61memo
Registered User
 
Join Date: Jan 2013
Location: san diego
Posts: 29
12 bolt chevy diff

What would be an ideal gear ratio for my 66 burban 12 bolt diff,original 3 speed manual tranny 235/75/15 tire looking for highway cruising and not to bad city trying to get the best of both worlds ...thanks for any info
61memo is offline   Reply With Quote
Old 01-25-2013, 01:00 AM   #2
HugoV
Registered User
 
Join Date: Sep 2012
Location: Seattle, WA
Posts: 65
Re: 12 bolt chevy diff

I would also like to know.
Posted via Mobile Device
HugoV is offline   Reply With Quote
Old 01-25-2013, 02:22 AM   #3
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: 12 bolt chevy diff

That depends on how you are using your truck. Are you using it like a truck or is it mainly a cruiser? what engine do you have? The 3.42 gears will still give you some decent pulling power. The 3.07's will be better for highway driving, but you will sacrifice some low end pulling ability. Either way, you will need to change the carrier if you have 3.73's or lower.
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE
Captainfab is offline   Reply With Quote
Old 01-25-2013, 01:30 PM   #4
LVPhotos
Registered User
 
LVPhotos's Avatar
 
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,857
Re: 12 bolt chevy diff

http://adamsdriveshaft.com/measurements_chart

http://adamsdriveshaft.com/
Here a gear chart from the guys I use. A 3.73 with a 235/75/15 (28") tire is in the sweet spot. Any higher would improve gas milage. Lower more power. I have 295/45/18 on the rear now 28" with 3.73 posi 12 bolt and it will run all day in fourth. Its the advantage of the 5th gear overdrive to pass gas stations.
__________________
1962 shortbed 408cui small block, TKO 600 5-speed, bagged Porterbuilt suspension. 18" Salt Flats
http://www.cardomain.com/ride/332579...t-c-k-pick-up/
http://67-72chevytrucks.com/vboard/s...d.php?t=560081
LVPhotos is offline   Reply With Quote
Old 01-25-2013, 02:01 PM   #5
Lugnutz65
Registered User
 
Lugnutz65's Avatar
 
Join Date: Jan 2013
Location: Columbia, SC
Posts: 1,927
Re: 12 bolt chevy diff

Quote:
Originally Posted by LVPhotos View Post
http://adamsdriveshaft.com/measurements_chart

http://adamsdriveshaft.com/
Here a gear chart from the guys I use. A 3.73 with a 235/75/15 (28") tire is in the sweet spot. Any higher would improve gas milage. Lower more power. I have 295/45/18 on the rear now 28" with 3.73 posi 12 bolt and it will run all day in fourth. Its the advantage of the 5th gear overdrive to pass gas stations.
So it sounds like you have a T5 tranny maybe?
__________________
My 65 C10 build: www.lugnutz65chevystepside.weebly.com

Want to know more about T5 transmissions? My website has a T5 Info Page and a Step by Step T5 rebuild.
Lugnutz65 is offline   Reply With Quote
Old 01-25-2013, 02:21 PM   #6
LVPhotos
Registered User
 
LVPhotos's Avatar
 
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,857
Re: 12 bolt chevy diff

Quote:
Originally Posted by Lugnutz65 View Post
So it sounds like you have a T5 tranny maybe?
Yes indeedee. Though an after thought the T-5 was never intened to use the torque 425+ to the rear. It is however using the factory bellhouse with motor mounts and the side engine mounts which helps the twist. The aluminum housing is its weak point.
__________________
1962 shortbed 408cui small block, TKO 600 5-speed, bagged Porterbuilt suspension. 18" Salt Flats
http://www.cardomain.com/ride/332579...t-c-k-pick-up/
http://67-72chevytrucks.com/vboard/s...d.php?t=560081
LVPhotos is offline   Reply With Quote
Old 01-25-2013, 05:05 PM   #7
61memo
Registered User
 
Join Date: Jan 2013
Location: san diego
Posts: 29
Re: 12 bolt chevy diff

Thanks for the info my 66 suburban is going to be a cruiser.what year diff can I use that i would be able to install 3.42s or 3.08 keep in mind my burban is a six lug bolt pattern thanks once again for you help and my engine is the original 283 v8

Last edited by 61memo; 01-25-2013 at 05:16 PM.
61memo is offline   Reply With Quote
Old 01-25-2013, 05:11 PM   #8
61memo
Registered User
 
Join Date: Jan 2013
Location: san diego
Posts: 29
Re: 12 bolt chevy diff

I forgot to add to my thread a diff that i dont have to change the carrier
61memo is offline   Reply With Quote
Old 01-26-2013, 01:57 AM   #9
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: 12 bolt chevy diff

It doesn't have anything to do with the year. You will have to find a '63 to early '70 12 bolt that already has 3.07 gears.

With the 283 not producing much torque, you might be better off with the 3.42 gears. I just am not familar with the 1st gear, gear ratio in those 3 speeds. If you can find a 12 bolt with 3.07's, give it a try and see how well you like it.


Quote:
Originally Posted by 61memo View Post
Thanks for the info my 66 suburban is going to be a cruiser.what year diff can I use that i would be able to install 3.42s or 3.08 keep in mind my burban is a six lug bolt pattern thanks once again for you help and my engine is the original 283 v8
Quote:
Originally Posted by 61memo View Post
I forgot to add to my thread a diff that i dont have to change the carrier
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE
Captainfab is offline   Reply With Quote
Old 01-26-2013, 07:52 AM   #10
61_FL_Apache
Who Me?
 
61_FL_Apache's Avatar
 
Join Date: Sep 2010
Location: Royal Palm Beach, FL
Posts: 4,067
Re: 12 bolt chevy diff

I have a 3.07 in mine running 215/70/15's with a TH350 and wish I had a more taller gear in it. I plan for a taller tire next go round to get more out of it.

Between your tire size and mine, you will lose almost 6 mph just from different tires sizes.

This a tool I use to determine that.

http://www.miata.net/garage/tirecalc.html
__________________
Steve

1997 Tahoe LT 4D 2WD (DD)
2001 Blazer 4D 2WD
1961 Apache 10 (sold)
1965 C10 Stepper (sold)
61_FL_Apache is offline   Reply With Quote
Old 01-27-2013, 02:58 PM   #11
61memo
Registered User
 
Join Date: Jan 2013
Location: san diego
Posts: 29
Re: 12 bolt chevy diff

Thank you all for your info as far as finding a 63 to 70 diff with 3.07 s no luck and adding 3.07s to my diff around 800 dlls but there is tons of newer rear diffs six lug bolt pattern that is why I asked. Hey 61 FL APACHE how well do you do on the freeway with your combo on your truck(3.07s and 350 tranny and 215/70/15) thanks once again for your help
61memo is offline   Reply With Quote
Old 01-28-2013, 01:28 AM   #12
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: 12 bolt chevy diff

The '88 and up differentials are going to be about 3" wider than the differential you have now. Plus there will be cutting and welding involved in installing one under your truck

Quote:
Originally Posted by 61memo View Post
Thank you all for your info as far as finding a 63 to 70 diff with 3.07 s no luck and adding 3.07s to my diff around 800 dlls but there is tons of newer rear diffs six lug bolt pattern that is why I asked. Hey 61 FL APACHE how well do you do on the freeway with your combo on your truck(3.07s and 350 tranny and 215/70/15) thanks once again for your help
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE
Captainfab is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 09:27 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com