• Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

31 vs. 28 spline vs. 7.5 vs. 8.8 vs. 9?

  • Thread starter Thread starter screamin gt
  • Start date Start date Mar 23, 2008

screamin gt

5 Year Member
Apr 9, 2007
393
6
28
central CT
Mar 23, 2008
#1
  • Mar 23, 2008
  • #1
I know most if not all mustangs are 8.8 rear ends, but who has what for (28 or 31)spline? and just wondering what ever came with a 7.5 rear end? and the advantage of a 9" over the 8.8? and if anything came with a 9" from the factory?

just wondering....
 
B

bdcardinal

tree hugger
Jun 10, 2003
3,612
16
69
santa barbara, CA
Mar 23, 2008
#2
  • Mar 23, 2008
  • #2
v6's had the 7.5". GT's and cobras had the 8.8". they were all 28 spline except for 00 cobra R, 03-04 cobra and 05+ mustang GT.
 

Mustang92

SN's #1 1%er
Jun 6, 2001
6,467
2
79
South Florida
Mar 24, 2008
#3
  • Mar 24, 2008
  • #3
9" rears came in older ford trucks and some cars. They are stronger than an 8.8" but honestly there are cars running into the 8's on a built 8.8 so unless you are planning on some really big power they aren't worth it. 9" rears also weigh more so you have more rotating mass.

Bill
 

StangYellow

Founding Member
Sep 11, 2002
1,052
1
39
Mar 24, 2008
#4
  • Mar 24, 2008
  • #4
In addition to what Mustang92 said, the ford 9 inch is deemed indestructable. You can find a used one for a few hundred, while upgrading 8.8 will run you double that. If you have some sort of project in the works, a 9 inch is a great rear end. 7.5's are like tits on a bull...
 

screamin gt

5 Year Member
Apr 9, 2007
393
6
28
central CT
Mar 24, 2008
#5
  • Mar 24, 2008
  • #5
good info! thanks guys.

like I said though, not starting a project, just getting gears and was wondering more less what vehicles had what.
 

Mustang92

SN's #1 1%er
Jun 6, 2001
6,467
2
79
South Florida
Mar 25, 2008
#6
  • Mar 25, 2008
  • #6
StangYellow said:
In addition to what Mustang92 said, the ford 9 inch is deemed indestructable. You can find a used one for a few hundred, while upgrading 8.8 will run you double that. If you have some sort of project in the works, a 9 inch is a great rear end. 7.5's are like tits on a bull...
Click to expand...

Well just to clarify for those that may think that just because it's stated the 9" is cheap it's not as simple as finding a used 9" and tossing it in. Most have to be cut down to fit our cars and have drum brakes, they also do not have the same suspension mounts as the Mustang. So by the time you cut the housing down, add the correct suspension mounting brackets, convert to disk brakes, get custom axles you have far exceeded what it costs to build up an 8.8 rear.

Weld the axle tubes $75-150 depending on the shop.
31 spline axles $200-250.
31 spline differential $250-400 depending on what you go with.
Rear end girdle $150-200.

You can probably even come in under that price if you shop around, go with a ford T-loc built with extra clutches.

Bill
 

screamin gt

5 Year Member
Apr 9, 2007
393
6
28
central CT
Apr 3, 2008
#7
  • Apr 3, 2008
  • #7
no one mentioned the difference between 28 and 31 splines? I know the difference but what vehicles came with which? we have 28 spline right?
 

Mustang92

SN's #1 1%er
Jun 6, 2001
6,467
2
79
South Florida
Apr 3, 2008
#8
  • Apr 3, 2008
  • #8
Yes we have 28's.

Bill
 

BurningRubber

10 Year Member
Dec 6, 2004
1,865
24
58
Apr 3, 2008
#9
  • Apr 3, 2008
  • #9
The 8.8 is a very stout axle.

Even stock 28 spline shafts will take alot of abuse. Sure there are some that fall short, but that happens with every part, on every vehicle. In general they are stout.

I have no worries about breaking mine when I romp on my car.

Full bearing kits arent that expensive, so if you take it apart to swap a 31 spine differential and shafts I highly reccomend changing the bearings also.


I know MANY guys from the Jeep world (my other vehicular passion) swap in Ford 8.8's into their offroad rigs that are turning 33, 35, and larger inch tires. They get them from Explorers and Rangers, its a fairly un-involved swap and they RARELY break them... and I garuntee you the stresses off offroading are equal to or exceed what an axle sees making a pass down the drag strip.
 

Mossberg

Active Member
Jul 21, 2003
0
1
36
ATL, Shawty
Apr 3, 2008
#10
  • Apr 3, 2008
  • #10
Yeah, I did not have any issues with my 28 spline setup. I swaped to a 31 spline setup though since my car will eventually get blown and make passes down the 1320.
 
You must log in or register to reply here.

Similar threads

J
2004 Mustang 3.8L V6 vibrations above 65 MPH and differential leaks
  • joeybuddy96
  • Mar 16, 2026
  • SN95 V6 Mustang Tech
Replies
16
Views
588
SN95 V6 Mustang Tech Jul 14, 2026
joeybuddy96
J
Progress Thread The Mach Returns - Update/build thread
  • squeak93
  • Feb 20, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
5
Views
350
1996 - 2004 SN95 Mustang -General/Talk- Jun 1, 2026
squeak93
new :poo: box, may need to hit you guys up for 79-82 info when i fix thIs turd.
  • rednotch
  • Sep 27, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2 3
Replies
40
Views
2K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Apr 4, 2026
Noobz347
T
New Guy from Southeast Missouri
  • tcooke11
  • Jan 10, 2026
  • The Welcome Wagon
Replies
1
Views
268
The Welcome Wagon Jan 17, 2026
TomcatPC
J
For Sale MASTER LISTING: Abandoned '66 Mustang Restomod Part-Out (Wilwood, Ididit, Quick Performance, Mishimoto)
  • JasonB66
  • Thursday at 2:26 PM
  • Suspension
Replies
0
Views
51
Suspension Thursday at 2:26 PM
JasonB66
J
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?