Posi Rear for my 1971 LeMans - 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 03-06-2005, 05:03 PM
Registered User
 
Join Date: Mar 2005
Location: York, PA
Age: 59
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Posi Rear for my 1971 LeMans

New member here, hoping to get some benefit from your collective knowledge.
I have a 71 LeMans with a 350, and 350 TH Trans.
I recently added a dual plane manifold, Holley 600, HEI distributor and a mild hydraulic cam. (1000 - 5500RPM range)
What would be the reccomended tire size and rear end ratio, for use a s a daily driver?
I have an open rear now, and would like to install an aftermarket posi unit, but don't know if I have a B-O-P rear or a Chevy rear.
Any help is appreciated
Thanks

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 03-06-2005, 08:34 PM
Holder350's Avatar
Auto Parts Professional
 
Last photo:
Join Date: Feb 2005
Location: Whitesburg, TN
Posts: 1,037
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
First thing you need to find out is what rear-end yoy have in the car...like a 8.5 10 bolt or what ever. A good rear gear would be a 3.55 or a 3.73 if you want a redlight to redlight racer, that is and still be mildly steetable. As for the posi unit you would be better off to get a detroit locker unit to bolt in.

Holder350......
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 03-07-2005, 03:36 PM
Registered User
 
Join Date: Mar 2005
Location: York, PA
Age: 59
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Holder350,
The rear is a 10 bolt open rear (I believe 8.5), but as I said , I don't know how to tell if it is a Chevy or a B-O-P. From the info I have seen on-line the after-market posi units are different. I thought 3.55 would be a good streetable rear, just did not know if I should go higher(3.73, 4.10, etc)
Thanks
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 03-07-2005, 08:32 PM
M&M CUSTOM's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Transmission identification
Last journal entry: 1988 Suburban, the project continues.
Last photo:
Join Date: Mar 2003
Location: Northwest Pennsylvania.
Age: 42
Posts: 2,230
Wiki Edits: 9

Thanks: 0
Thanked 1 Time in 1 Post
You want streetable gears with a TH-350 and are open to tire size.
Shoot for a 26 to 28 inch tire, each 1/2 inch in height equals roughly 1/2 mile per hour speed difference.

Try for a combination that gives you a good range for takeoff and highway, something similar to a 3.42 gear at most and and more toward the 27 to 28 inch tire size, 235/75/15 measures close to 29 inches for reference.

(Section width in mm) / (25.4 mm per inch) X (sidewall height ratio) X (2 the tire on top of, and bottom of the rim) + (15, the mmeasurement of the rim) = the tire diameter size in inches.
235, divided by 25.4, times .75, times 2, plus 15, equals 28.87795 inches.

And remember not all tire manufacturers tires of the same posted sidewall size will measure the same as other manufacturers tires.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 03-08-2005, 05:49 AM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
If your rearend is stock it is either a BOP 8.25" 10-Bolt (not to be confused with the Chevy 8.2") or the corporate 8.5". '71 was the transition year for the 10 bolts in many models of GM. Either one is good enough for a mild street car. 3.55 gears would be just about ideal for you combo, especially if you wanted to slip a 200-4R in place of the TH350 later on. A 3.73 or 4.10 is a "lower" ratio and you do NOT need anything that low for a mild street Pontiac. Even a real healthy Pontiac will work good with a 3.55.


I had a '67 GTO years ago with the 335HP "YS" 400, TH400 and 3.55 8.25" Posi. I had bored the 400 .030" over, added a Cam Dynamics Stage II Hyd. cam, Torker, headers, etc. and had the trans rebuilt with all B & M innards. It would break the tires loose on a full throttle 2-3 shift and I don't mean "chirp" the tires, I mean break 'em loose. The stock 10 bolt held up just fine. That car was my daily driver for 2 years and my "toy" for another 1-1/2 years, I put 35,000 HARD miles on it in that time, many of those 1/4 mile at a time.
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
Rear end swap required & I'm cunfussed datsun dale Transmission - Rearend 8 12-17-2008 09:03 AM
Rear end swap problems datsun dale Transmission - Rearend 1 12-17-2002 10:50 PM
Rear end Buffed Engine 3 10-31-2002 05:11 AM
Independant rear for 1971 Nova KING_NOVA Transmission - Rearend 1 10-24-2002 05:32 PM
1971 Buick GS350 10 bolt Posi elcamino Transmission - Rearend 0 10-13-2002 04:10 PM


All times are GMT -6. The time now is 10:49 PM.


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.