GM 8.5 inch 10-bolt upgrade - 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 08-12-2006, 07:59 PM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
GM 8.5 inch 10-bolt upgrade

I just learned that I have a 8.5 inch, 10-bolt, 2.73 ratio in my 72 nova. I checked the casting number to verify it.

I read in some hot rod article that some of the GM 8.5" 10-bolt setups are very strong and can be used up to like 800 HP and 9 second quarter mile times. I have a copy of that article. I guess it's the ones with the heavier larger ring gear bolts.

If that is what I have, can't I just change the ring/pinion gear setup to a lower gear like a 3.73 or a 4.11 and keep the entire axle housing and maybe even the axles? I mean why upgrade the entire unit spending a small fortune when I can basically change the guts. Please help me out because I am new at this rear end stuff.

I have a 468 BB Chevy at about 550 HP with a Turbo 350 trans with a shift kit. My goal is really to just change the gear to a lower one (currently a 2.73) which sucks for street racing (good for gas mileage - but who cares) I just want to race it on the street. this is not a drag racing car running 7000 rpm all the time. most time is spent below 3000 rpm.

thanks.

lee

    Advertisement

Last edited by leejoy; 08-13-2006 at 06:20 AM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 08-12-2006, 08:13 PM
Registered User
 
Last photo:
Join Date: Nov 2004
Location: Cali
Posts: 994
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Are you referring to the 8.5" 10-bolt rear that came in the 70's Novas?
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 08-12-2006, 08:14 PM
1969NovaSS's Avatar
turbo lag......yeeeeehaaaaaaw
 
Last photo:
Join Date: Feb 2005
Location: oxnard,ca
Age: 27
Posts: 684
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
10.5"? Are you sure you dont have a 8.5 10bolt rear? gm did make a 10.5 I believe but it was used only in the 1 ton trucks I think. the 8.5's are good rear ends. they have the same spline axles as the 12 bolts and they have pleny of parts for them.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 08-12-2006, 10:13 PM
67 Deuce 4 Me's Avatar
Bowtie or Die!
 
Last photo:
Join Date: Dec 2004
Location: TN
Age: 43
Posts: 637
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
If its an 8.5 10 bolt. Its also referred to as a "corporate" not sure why maybe because GM built so many?! There very good rear ends. Is it a limited slip or open diff? Yes you can change the gear quite easily. But if you have no experience doing this you can screw up big time. You must know how to set up the gears back lash, pinion depth, checking gear pattern etc.Some guys get lucky and no noise.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 08-13-2006, 06:13 AM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by onovakind67
Are you referring to the 8.5" 10-bolt rear that came in the 70's Novas?
sorry - brain cramp. too much beer and Cocoa Puffs.

Yes - the 8.5" 10-bolt.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 08-13-2006, 06:18 AM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by 67 Deuce 4 Me
If its an 8.5 10 bolt. Its also referred to as a "corporate" not sure why maybe because GM built so many?! There very good rear ends. Is it a limited slip or open diff? Yes you can change the gear quite easily. But if you have no experience doing this you can screw up big time. You must know how to set up the gears back lash, pinion depth, checking gear pattern etc.Some guys get lucky and no noise.
dear Duece:

yes it is a limited slip. the guy I bought it from a few years back said so, and I've done many burnouts and stuff and it's true. both tires grip. so back to my original question: can I just change the guts to a lower gear and keep the axles and housing and stuff? what's all this I hear about C-clip eliminators. should I do that as well - why? can you suggest a brand name to choose for the ring/pinion setup I should go with. Can I keep the carrier parts and just change the ring/pinion?

I am buying a DVD on how to rebuild these things. I will watch that first, plus read some articles before attemting to do it myself.

thanks.

Lee
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 08-13-2006, 02:42 PM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
yes, that is a stout rear end. The pinion gear shaft is same size as in a 12 bolt and the ring gear is only 3/8 smaller diameter. If you can, have a welding shop weld the joints where the axle tubes join the center section. Change your rear gears to the ratio you desire and have a blast.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 08-13-2006, 08:57 PM
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
Sometimes the spring perches can use a little extra welding, too. It's also not a bad idea to use two U-bolts on each side instead of the T-bolts.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 08-14-2006, 10:32 AM
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: 43
Posts: 2,231
Wiki Edits: 9

Thanks: 0
Thanked 1 Time in 1 Post
After reading the context of the thread I changed the title to read correctly.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 08-16-2006, 06:15 PM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by cool rockin daddy
yes, that is a stout rear end. The pinion gear shaft is same size as in a 12 bolt and the ring gear is only 3/8 smaller diameter. If you can, have a welding shop weld the joints where the axle tubes join the center section. Change your rear gears to the ratio you desire and have a blast.
good news. that's what I was looking to hear. can I keep the axles or do they "need" to get replaced. what about C-clip elimination? necessary or not.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 08-16-2006, 06:16 PM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by M&M CUSTOM
After reading the context of the thread I changed the title to read correctly.
how did you do that?
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 02-05-2009, 06:08 AM
Registered User
 
Join Date: Feb 2009
Location: Sayre,PA
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
8.5 10bolt

I just got done rebuilding my 8.5 10 bolt rear end out of my 81 camaro. A good upgrade if you can find one is a caprice cop car rear end. It had a positraction with 30 spline axles my stock were 28 spline, gears were 323s which I changed over to 390s I had to get axles made for it from Moser which were 265.00 shipped to the door. Also if you want to put disc brakes on the rear with out spending 400.00 bucks on the kit they sell. I went with 2001 chevy s10 rotors which also have the emergancy brake drums if you want to use them there also 11 1/2 inches in diameter they just fit and im running a 15" rim on rear. calipers and pads are from a Monte carlo and i bought GM metric weld on caliper brackets. To get your brackets straight when you weld them assemble everthing and make a fitting to screw into your caliper and just apply shop air to it so caliper is locked onto you rotor and it wont move make a few tacs. I had around 175.00 changing it to disc i went with the best pads and rotors could have been a few dollors cheaper.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 02-05-2009, 03:18 PM
junior stocker's Avatar
Registered User
 
Join Date: Feb 2004
Location: Everett, Washington
Age: 62
Posts: 820
Wiki Edits: 0

Thanks: 0
Thanked 10 Times in 9 Posts
10 bolt rear end

Are you absolutely sure it's an 8.5" 10 bolt, and NOT an 8.2" 10 bolt? They look similar, but parts, other than brakes, and maybe axles, do not interchange. In an article from HOT ROD- May 1997, "The 10-Bolt Tango" it states, "the 64-72 10-bolt in the Camaro, Chevelle, and NOVA measures 8.2 inches across the ring gear, so stay away from that one too". Meaning the 8.2 is weak, not only because of the ring gear size, but mostly because the pinion gear shaft is smaller than the 8.5" unit. The 8.5" AND 12 bolt share the same size pinion gear shaft diameter of 1.625" diameter. It does'nt report what the diameter is on the 8.2.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 02-05-2009, 03:24 PM
SSedan64's Avatar
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Macon, GA.
Age: 50
Posts: 6,016
Wiki Edits: 0

Thanks: 0
Thanked 46 Times in 46 Posts
Quote:
Originally Posted by junior stocker
Are you absolutely sure it's an 8.5" 10 bolt, and NOT an 8.2" 10 bolt? They look similar, but parts, other than brakes, and maybe axles, do not interchange. In an article from HOT ROD- May 1997, "The 10-Bolt Tango" it states, "the 64-72 10-bolt in the Camaro, Chevelle, and NOVA measures 8.2 inches across the ring gear, so stay away from that one too". Meaning the 8.2 is weak, not only because of the ring gear size, but mostly because the pinion gear shaft is smaller than the 8.5" unit. The 8.5" AND 12 bolt share the same size pinion gear shaft diameter of 1.625" diameter. It does'nt report what the diameter is on the 8.2.
The 10-Bolt 7.5", 8.2" & 12-Bolt 8.875" Truck rear have 1.438" Pinion dia.
7.5" has 27 spline, 8.2" = 25 spline, 12-Bolt truck = 30 spline pinions.

Last edited by SSedan64; 02-05-2009 at 03:30 PM.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 02-05-2009, 04:44 PM
prostreet6t9's Avatar
Differential/Driveline
 
Last photo:
Join Date: Sep 2008
Location: oregon
Age: 51
Posts: 1,719
Wiki Edits: 0

Thanks: 5
Thanked 40 Times in 37 Posts
Quote:
Originally Posted by leejoy
I just learned that I have a 8.5 inch, 10-bolt, 2.73 ratio in my 72 nova. I checked the casting number to verify it.

I read in some hot rod article that some of the GM 8.5" 10-bolt setups are very strong and can be used up to like 800 HP and 9 second quarter mile times. I have a copy of that article. I guess it's the ones with the heavier larger ring gear bolts.

If that is what I have, can't I just change the ring/pinion gear setup to a lower gear like a 3.73 or a 4.11 and keep the entire axle housing and maybe even the axles? I mean why upgrade the entire unit spending a small fortune when I can basically change the guts. Please help me out because I am new at this rear end stuff.

I have a 468 BB Chevy at about 550 HP with a Turbo 350 trans with a shift kit. My goal is really to just change the gear to a lower one (currently a 2.73) which sucks for street racing (good for gas mileage - but who cares) I just want to race it on the street. this is not a drag racing car running 7000 rpm all the time. most time is spent below 3000 rpm.

thanks.

lee
Your best chance on having a 8.5 hold up is using a aftermarket carrier and axles. The stock open and Posi carrier's like to break the carrier brg hub on the ring gear side.

A 9 second car leaves the line pretty hard and I'm not sure how long a 8.5 will hold up to that. With limited traction on the street it might stay in one piece for a while.
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
10 bolt rear end question 8.2 or 8.5 ?? nheron Transmission - Rearend 6 03-02-2008 08:16 PM
8.5 chevy 10 bolt Dragster13 Transmission - Rearend 6 12-03-2005 03:07 PM
gm 10 bolt series I.d. tkett32 Transmission - Rearend 6 07-03-2005 07:16 PM
gm 10 bolt 8.5 jo5hi3 Transmission - Rearend 2 12-17-2003 05:51 PM
gm 10 bolt axle, bearings. hepcat Transmission - Rearend 4 09-20-2003 08:36 AM


All times are GMT -6. The time now is 10:18 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.