12 bolt (truck rear end) questions - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 02-09-2009, 09:41 PM
It's all in the reflexes
 
Last photo:
Join Date: Feb 2009
Location: Ritzville, Washington
Age: 21
Posts: 32
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
12 bolt (truck rear end) questions

Hello I'm new here and had a tech question. I have a 73 GMC 1/2 ton truck with a 355 (400 horsepower) and a turbo 350 with a 2600 stall. It has a 12 bolt 8.875 rear end. I'm not sure of the gear ratio but I know it doesn't have posi. Are these rear ends as good or better than a cars? And what would be the best rear end gears to put in it? Thanks alot
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-11-2009, 03:48 AM
Member
 
Last photo:
Join Date: May 2003
Location: Shreveport LA
Age: 64
Posts: 5,103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
It's a good rear end. If you're sure it's not posi, here's how to find the ratio:

Block a front wheel so it won't roll. Put the transmission in neutral. Jack up one of the back wheels, not both, just one. Sit where you can see the rear U-joint and reach the valve stem of the raised wheel at the same time. Put the valve stem at the 6:00 position. Slowly turn the wheel TWO full turns while counting the revolutions of the U-joint. If it turns over 2-3/4 times, it's a 2.73 or 2.76 ratio, or something real close. If it turns a little over 3 turns, it's 3.08 or 3.07. 3-3/4 turns = 3.73, etc., etc., etc.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-11-2009, 03:47 PM
It's all in the reflexes
 
Last photo:
Join Date: Feb 2009
Location: Ritzville, Washington
Age: 21
Posts: 32
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Yea my grandpa told me to do that so I should...Whats the difference between a 3 carrier and a 4 carrier?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-11-2009, 05:14 PM
Deuce's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Choosing a trailer
Last journal entry: Jan 13 2013
Last photo:
Join Date: Aug 2002
Location: Deuceland USA
Age: 65
Posts: 5,657
Wiki Edits: 6

Thanks: 0
Thanked 9 Times in 9 Posts
Different carriers ... carry a different range of gear ratios.



This is a series 3 carrier ...
The area where the gear attaches is thicker on a different series
__________________


"I won't be wronged . I won't be insulted, and I won't be laid a hand on. "






Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-11-2009, 06:52 PM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: 1999-2001: Getting it on the road
Last photo:
Join Date: Dec 2005
Location: Pittsburgh, PA
Age: 40
Posts: 5,128
Wiki Edits: 16

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by Dylanic_350
Hello I'm new here and had a tech question. I have a 73 GMC 1/2 ton truck with a 355 (400 horsepower) and a turbo 350 with a 2600 stall. It has a 12 bolt 8.875 rear end. I'm not sure of the gear ratio but I know it doesn't have posi. Are these rear ends as good or better than a cars? And what would be the best rear end gears to put in it? Thanks alot
They are a touch weaker than car 12-bolts, but not much. The pinion input shaft is the same size as an 8.5" 10-bolt, but its rarely what breaks.
Reply With Quote Quick reply to this message

Recent Transmission - Rearend posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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 for yourself.
Email Address:

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.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
this is a saver.... GM build codes TooMany2count General Rodding Tech 24 11-23-2009 09:36 AM
12 bolt posi rear end fluid 1972bigblockchev Transmission - Rearend 3 06-19-2007 09:46 AM
questions about swapping R/E gears from a 12 bolt Gm into a Pontiac 10 bolt housing l Bad Rat Transmission - Rearend 6 06-11-2007 10:50 AM
12 bolt rear end question Roy_67_SS350 Transmission - Rearend 3 01-04-2004 06:12 AM
Question about 12 bolt rear end Roy_67_SS350 Transmission - Rearend 6 12-14-2003 11:57 AM


All times are GMT -6. The time now is 01:15 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.