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 1947 - 1959 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 04-15-2018, 06:59 PM   #1
62 Barnfind
Registered User
 
62 Barnfind's Avatar
 
Join Date: Jan 2012
Location: Killeen, Tx
Posts: 1,344
GM 7.5 rear axle

I picked up a 70's era gM 7.5 axle today. I know it's probably not the ideal axle but the price was good and the length, (60in) and the bolt pattern (5x4.75) was right. Has anybody used this axle in a swap before in a 55-59? Just wanted to know if it will work or do I need something else. I will be running about 300 hp and from what I read the axle will be fine. I want to be able to drive long distances with it. Thanks!

__________________
John Z
1962 Chevy C10 Stepside
62 Barnfind
My build tread: http://67-72chevytrucks.com/vboard/s...d.php?t=507513

Last edited by 62 Barnfind; 04-15-2018 at 07:21 PM.
62 Barnfind is offline   Reply With Quote
Old 04-15-2018, 07:35 PM   #2
cal1320
Registered User
 
Join Date: Oct 2010
Location: Central FL
Posts: 2
Re: GM 7.5 rear axle

Im running a 7.5'' from an 87 Camaro in my 56. Ive logged almost 20K miles on it. It is what it is. A weak axle that wont tolerate large amounts of HP when mixed with good traction. I also have a 4cyl S10 T5 trans, so that keeps me from hammering on it.
cal1320 is offline   Reply With Quote
Old 04-15-2018, 07:39 PM   #3
62 Barnfind
Registered User
 
62 Barnfind's Avatar
 
Join Date: Jan 2012
Location: Killeen, Tx
Posts: 1,344
Re: GM 7.5 rear axle

Quote:
Originally Posted by cal1320 View Post
Im running a 7.5'' from an 87 Camaro in my 56. Ive logged almost 20K miles on it. It is what it is. A weak axle that wont tolerate large amounts of HP when mixed with good traction. I also have a 4cyl S10 T5 trans, so that keeps me from hammering on it.
From what I read 330 HP is about the max. i'll be running a 5.3 but no upgrades. I just want to go down the road without having a screaming engine.
__________________
John Z
1962 Chevy C10 Stepside
62 Barnfind
My build tread: http://67-72chevytrucks.com/vboard/s...d.php?t=507513
62 Barnfind is offline   Reply With Quote
Old 04-15-2018, 08:33 PM   #4
cal1320
Registered User
 
Join Date: Oct 2010
Location: Central FL
Posts: 2
Re: GM 7.5 rear axle

70s era axles had numerically low gears because overdrive wasnt currently offered. Thats what you want if you dont have overdrive. Check the ratio. It could be anything from a 3.08 down to a 2.56 . Mine was from the od era and is a 3.42
cal1320 is offline   Reply With Quote
Old 04-15-2018, 08:44 PM   #5
62 Barnfind
Registered User
 
62 Barnfind's Avatar
 
Join Date: Jan 2012
Location: Killeen, Tx
Posts: 1,344
Re: GM 7.5 rear axle

Quote:
Originally Posted by cal1320 View Post
70s era axles had numerically low gears because overdrive wasnt currently offered. Thats what you want if you dont have overdrive. Check the ratio. It could be anything from a 3.08 down to a 2.56 . Mine was from the od era and is a 3.42
I don't know what year its from or the gear yet . I will have OD on this truck.
__________________
John Z
1962 Chevy C10 Stepside
62 Barnfind
My build tread: http://67-72chevytrucks.com/vboard/s...d.php?t=507513
62 Barnfind is offline   Reply With Quote
Old 04-15-2018, 10:19 PM   #6
joedoh
Senior Member
 
joedoh's Avatar
 
Join Date: May 2007
Location: Doodah Kansas
Posts: 7,746
Re: GM 7.5 rear axle

Quote:
Originally Posted by 62 Barnfind View Post
From what I read 330 HP is about the max. i'll be running a 5.3 but no upgrades. I just want to go down the road without having a screaming engine.

you could probably have a lot more hp on a 7.5 as long as you dont have a lot more traction. every 7.5 I have seen with problems was from hooking up, not spinning, and with 330hp without any weight over the rear you will be spinning most of the time. I think you will be fine.
__________________
the mass of men live lives of quiet desperation


if there is a problem, I can have it.

new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393
joedoh is offline   Reply With Quote
Old 04-15-2018, 11:24 PM   #7
PDW HOTRODS
Registered User
 
PDW HOTRODS's Avatar
 
Join Date: Nov 2006
Location: Sutherlin Oregon
Posts: 493
Re: GM 7.5 rear axle

They used it in Camaro's with V8's for years. Even Z28's had it. If you take off hard with sticky tires it might brake. Should be fine for normal use.
PDW HOTRODS is offline   Reply With Quote
Old 04-16-2018, 08:25 AM   #8
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: GM 7.5 rear axle

It's really about the torque more than the hp. A 7.5 with good traction against 400 ft/lbs loses, regardless of the rpm the engine's spinning.

Different gear ratios also make a difference. The ring and pinion ratio multiplies the torque coming into the rear end. 300 ft/lbs through 3.73 gears creates 1119 ft/lbs at the axles. But 400 ft/lbs through a 2.29 gear only creates 916 ft/lbs at the axles.

This is part of the reason why the 7.5 in my '79 Monte survived for 8 years behind a Buick 455. The 455 was only producing about 370 ft/lbs and the rear had 2.29 gears. When I replaced the axle it was due to wear at the axle bearing surface.

Last edited by 1project2many; 04-16-2018 at 08:43 AM.
1project2many is offline   Reply With Quote
Old 04-16-2018, 01:49 PM   #9
_Ogre
Registered User
 
_Ogre's Avatar
 
Join Date: Jan 2012
Location: Motown
Posts: 7,660
Re: GM 7.5 rear axle

Quote:
Originally Posted by PDW HOTRODS View Post
They used it in Camaro's with V8's for years. Even Z28's had it. If you take off hard with sticky tires it might brake. Should be fine for normal use.
agreed. 1000s of bbc camaro/firebird and trans am of the day had them
__________________
cool, an ogre smiley Ogre's 58 Truk build

how to put your truck year and build thread into your signature
shop air compressor timer
_Ogre is offline   Reply With Quote
Old 04-16-2018, 08:14 PM   #10
62 Barnfind
Registered User
 
62 Barnfind's Avatar
 
Join Date: Jan 2012
Location: Killeen, Tx
Posts: 1,344
Re: GM 7.5 rear axle

Thanks for the reply! I figured that it would be ok for what I'm doing. I can still be on the lookout if I find something better. I start tearing down this Saturday to get real for the suspension build. Pics will be coming!
__________________
John Z
1962 Chevy C10 Stepside
62 Barnfind
My build tread: http://67-72chevytrucks.com/vboard/s...d.php?t=507513
62 Barnfind is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

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 06:15 PM.


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