Swap a 8" to a 9" rear axle - Vintage Mustang Forums
 7Likes
Reply
 
Thread Tools
post #1 of 22 (permalink) Old 07-10-2019, 04:29 PM Thread Starter
Senior Member
 
Join Date: May 2014
Location: Berlin, Germany
Posts: 160
Swap a 8" to a 9" rear axle

Hi,


I would like to know if the 8" rear axel of my early 65 Mustang with a 289 (bored out to 306) and a C4 transmission can be easily swapped out against a 9" rear axle.


If not what needs to be changed?
philm3 is offline  
Sponsored Links
Advertisement
 
post #2 of 22 (permalink) Old 07-10-2019, 04:33 PM
Senior Member
 
Sparky66's Avatar
 
Join Date: Sep 2012
Location: Arlington, WA
Posts: 837
AFAIK, you'll need new spring perches and a new yoke/u-joint. Other than that, not sure.


1966 Restomod/track car, 1973 Q-code Mach 1, 1997 F250 diesel, 2000 VW Beetle Rallycross car, 2010 Crown Vic (ex-City of Lakewood PD), 2015 Focus ST-2
Sparky66 is offline  
post #3 of 22 (permalink) Old 07-10-2019, 04:37 PM
Senior Member
 
cmefly's Avatar
 
Join Date: Mar 2011
Location: Bonney Lake
Posts: 4,462
Buy something like this and use the small axle bearing ends. That way you can reuse your axles and brakes if you want to keep the cost down. You will need to buy the spring plates/shock plate and u bolts for the larger axle tubes. https://www.ebay.com/itm/9-Ford-Must...vmu6ZvjUcT-2jA

Last edited by cmefly; 07-10-2019 at 04:40 PM.
cmefly is online now  
 
post #4 of 22 (permalink) Old 07-10-2019, 04:41 PM
Senior Member
Supporting Member
 
Redneckgearhead's Avatar
 
Join Date: Jun 2013
Location: Sauk Centre MN.
Posts: 1,696
You would need to find a 9" of the correct width, 57.25" IIRC. If the spring perches are in the correct spot then it's a bolt in situation. But looking at your seemingly mild engine build there really is no need to swap. The 8" is typically good to 500 hp or so.

Scott

Never let the truth get in the way of a good story
Redneckgearhead is online now  
post #5 of 22 (permalink) Old 07-10-2019, 04:47 PM
Senior Member
 
66coupe289's Avatar
 
Join Date: Sep 2001
Location: Milwaukee (Sussex), WI
Posts: 2,097
8" & 9" refers to the ring gears within the center section of the rear end. Those gears themselves are not interchangeable. You need to replace the entire rear end housing, basically from wheel to wheel, including the center section. 9" rear ends are very popular for their strength, but likely overkill.

Chris (Sussex, WI)

California car born an I6, now with warmed up 289 w/T-5z, 3.55T-loc, Granada Discs and 6 bolt Moto-Lita Steering Wheel. Owned since 1983.
66coupe289 is offline  
post #6 of 22 (permalink) Old 07-10-2019, 05:00 PM Thread Starter
Senior Member
 
Join Date: May 2014
Location: Berlin, Germany
Posts: 160
My problem is as mentioned before I cant seem to find the housing including a fully rebuilt 8" cener section

Last edited by philm3; 07-10-2019 at 05:07 PM.
philm3 is offline  
post #7 of 22 (permalink) Old 07-10-2019, 05:13 PM
Senior Member
Supporting Member
 
Redneckgearhead's Avatar
 
Join Date: Jun 2013
Location: Sauk Centre MN.
Posts: 1,696
What are you trying to accomplish? Is the current rear axle an 8"? Is it making noise or indicating it needs rebuilt/repair?
Israel likes this.

Scott

Never let the truth get in the way of a good story
Redneckgearhead is online now  
post #8 of 22 (permalink) Old 07-10-2019, 05:30 PM
Senior Member
 
Garth66's Avatar
 
Join Date: May 2005
Location: San Jose, CA
Posts: 276
Quote:
Originally Posted by philm3 View Post
My problem is as mentioned before I cant seem to find the housing including a fully rebuilt 8" cener section
This statement makes it unclear what you're trying to accomplish, or why. So you don't have an 8" rearend axle? Do you have a rear axle at all? And why do you want to change from an 8" to a 9"? Will this be a drag car? Or do you just want more un-sprung weight in the rear end (not that anyone would)?

More info please...

________________________
66 Mustang GT Fastback
70 Mustang Mach 1
72 DeTomaso Pantera
69 Cutlass Convertible
Garth66 is offline  
post #9 of 22 (permalink) Old 07-10-2019, 05:30 PM Thread Starter
Senior Member
 
Join Date: May 2014
Location: Berlin, Germany
Posts: 160
Hi Scott,


my problem seems to be that the place where the axle shafts are pushed into the housing there is excessive play as can be seen on this video:




I have an 8" rear axle with a 2,80 ratio but that cant be found anywhere. Rebuilding this here in Germany is too expensive.

Last edited by philm3; 07-10-2019 at 05:34 PM. Reason: Adding more information
philm3 is offline  
post #10 of 22 (permalink) Old 07-10-2019, 05:59 PM
Senior Member
 
Smitten's Avatar
 
Join Date: Jan 2011
Location: West Melbourne FL
Posts: 1,307
Why do you feel you need a 9 inch? The 8 is is strong enough unless you are making serious power or are dumping the clutch at pretty high rpms. TJ on ebay make 8 inch rear that will handle most people's needs.

Sent from my SM-G935V using Tapatalk

Steve

64 1/2 D code 5 speed Coupe
07 GT 5 speed Vert

Plus 9 more that I no longer own!
Smitten is offline  
post #11 of 22 (permalink) Old 07-10-2019, 06:06 PM
Senior Member
 
Join Date: Mar 2001
Location: Tunkhannock PA
Posts: 19,604
That would be the spider gears making that noise not the ring and pinion. I’d suggest pulling the differential out and inspecting it to see what needs to be replaced.

You seem to be fixated on 2.80 gears. That ratio was not available in a 9” axle. The general ratios in a 9” would be 2.50, 2.75, 3.00, 3.25, 3.50 The 8” would be 2.79, 3.00, 3.25, 3.50. I wouldn’t think twice about going to 3.00. First though pull and inspect the differential and see what’s going on.

Tom

One thing great about getting older. A life in prison sentence is less of a deterrence

Huskinhano is offline  
post #12 of 22 (permalink) Old 07-10-2019, 06:34 PM
Senior Member
 
geicoman58's Avatar
 
Join Date: Apr 2012
Location: Annapolis,MD
Posts: 1,945
Are you sure that axle is installed all the way in? Can we see it from the side view? Some back and forth is normal on an older high mileage rear. Stick with what you have and repair it if something is broken. Someone offered you a core if I remember, get it and rebuild it your self with the help of utube. Or buy one rebuilt and ready to install from TJ. The 9 inch rebuild videos are basically the same for your 8 inch unit. Are you able to pull the center section third member if it is in fact broken internally?
geicoman58 is offline  
post #13 of 22 (permalink) Old 07-10-2019, 06:47 PM
Senior Member
 
22GT's Avatar
 
Join Date: Jun 2009
Location: Southeastern Pennsylvania
Posts: 33,628
You are better off fixing the axle you have, or at most replacing the "pumpkin".

If you want to upgrade to the 9", you'll need a 9" differential, and the correct housing for the 65-66. Yeah, I know the originals were different each of those years, but a repro will do. You'll need 9" axle housing brake lines, the correct hose for dual exhaust, and you'll need to have the driveshaft shortened about an inch IIRC. Your brakes, axles, cables, and U bolt/plate assemblies will do.


Amateur restorer. Well, sometimes I have been paid for it. But not right now.

Last edited by 22GT; 07-10-2019 at 06:50 PM.
22GT is offline  
post #14 of 22 (permalink) Old 07-10-2019, 06:49 PM
Senior Member
 
Join Date: Oct 2001
Location: Charlotte, NC
Posts: 795
If you can still find them, the 1957 Ford 9” rear end fits the 64-66 Mustang. The width is the same and thebperches are in the same location. Also, the late 70’s Lincoln Versailles 9” rear ends have the same perch width but overall width is 1/4” wider. You’ll need to change either driveshaft yoke or pinion yoke to with in your Mustang. Also, most Versailles rearends has 2 something gear ratios and aren’t great for a performance car. You’ll want to upgrade.


"Do it right the first time...it will cost you less in the long run."
289stang is offline  
post #15 of 22 (permalink) Old 07-10-2019, 07:06 PM
Junior Member
 
Join Date: Jun 2019
Posts: 21
Not trying to hijack the thread but related topic. I was told my car has a 9" rear end how do I confirm this? Supposedly from a Shelby
gen3 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Vintage Mustang Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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 On
Trackbacks are On
Pingbacks are On
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome