Does she have a nice rear end or what?


New Member
Nov 18, 2019
I have a rear end that may or may not be original to my 1969 Mustang. Engine and transmission are not original. Car came with a 302, but was replaced with a 351C. Transmission is a C4.

The differential is leaking, so I need a gasket at minimum, but I would sure like to know if I have a limited sllip, and what gear ratio is in there. There are lots of numbers in the casting, but no tag.

It is a 9" for sure. Any suggestions on how to identify what I have?
  • Sponsors(?)


SN Certified Technician
Apr 12, 2002
if you can get a socket on two of the lower pumpkin bolts, its not a 9".

as to whether or not its a limited slip diff, jack up one wheel, and with the trans in neutral try to turn it. if it turns easily then you have an open diff.


Slap me as well as point and laugh
May 17, 2018
Enterprise AL
With the wheels off the ground when you rotate one wheel the other should rotate in the same direction. If it does not I believe that is also an indication that it is open.

As for the ratio. Mark the wheel and mark the drive shaft. Rotate the drive shaft and count how many times you have to rotate it for the wheel to make one full rotation.

All of the above is true for a fox rear. I'm not sure how different the 9" is. Hope it helps.


New Member
Nov 18, 2019
Cool. I will do both of those things tomorrow. I still need to get a gasket tho. Which numbers on the casting would be the ones to look for? And is there any way to tell what year it is without the tag?

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
polk county florida
You are gonna pull the pumpkin to fix the leak anyway, the ring gear will tell you the ratio, the carrier will tell you open or not.
Thread starter Similar threads Forum Replies Date
999cm999 Does this 'Stang sound nice? 1996 - 2004 SN95 Mustang -General/Talk- 8
D Does anyone have a link to a nice detailed guide for A T5 swap? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 10
Seraphitia102 Does anyone have a link to some nice looking engine dress up kits? 1996 - 2004 SN95 Mustang -General/Talk- 3
D 05' does a nice burnout!! 2005 - 2009 Specific Tech 6
K How does this look in terms of a list of mods for my '04 3.9L v6 SN95 V6 Mustang Tech 9
silverlx50 Engine Does anyone have a picture of the O2 sensor harness orange ground wire? Fox 5.0 Mustang Tech 5
R 1995 Mustang power window does not work. 1996 - 2004 SN95 Mustang -General/Talk- 0
79pace 82GT Does not Crank the Starter with the Key 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 4
S vehicle shut of and does not want to start up again 2005 - 2009 Specific Tech 0
F Electrical Does EFI computer case need to grounded? Fox 5.0 Mustang Tech 22
Habu135 Fox : How Much Power Does a Stock 1993 Cobra Make? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 7
S Does Having a dead battery make the PCM fail? 2005 - 2014 S-197 Mustang -General/Talk- 0
M Brakes Does anyone know specific casting numbers on 1989 GT O.E. Calipers? Fox 5.0 Mustang Tech 11
G One coilpack not getting spark but does have power at wire SN95 4.6L Mustang Tech 3
C Does a 2015 Mustang have a radio code? 2015+ Specific Tech 0
J Does anyone know where this wire goes? Other Auto Tech 28
kiddiccarus Does anyone customize the interior of the 94-95? I am running into brick walls 1996 - 2004 SN95 Mustang -General/Talk- 0
T Need good/affordable cooling fan for Mach 1 that does not vibrate too much 1996 - 2004 SN95 Mustang -General/Talk- 3
S Where does this negative cable go??? 2005 - 2009 Specific Tech 3
9 What does the coil pack Capacitor do ? 1996 - 2004 SN95 Mustang -General/Talk- 3
Z Newbie question, Backup lights on 65. Does 12v for lights go thru neutral switch? 1965 - 1973 Classic Mustangs -General/Talk- 1
ndfox92 Fox does anyone have a victor efi intake for a 351w they want to part with? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 0
MrPerfect2 What does the idle sound like if timing is 14 vs 12 degrees 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 18
J 94 GT Convertible. What does this harness connect to? 1994 - 1995 Specific Tech 0
J Paint and Body Does my floorpan need replacing? Fox 5.0 Mustang Tech 8
A Does it make sence ? 2005 - 2014 S-197 Mustang -General/Talk- 1
90sickfox Does any one else wish the 18 amd 19 fog lights were lower ??? 2015+ (S550) Mustang -General/Talk 0
M Does anyone know what the hole to the left of the oil pressure sender is for?? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
J Does Ford Performance make 3.73 gear for v6 mustangs? 2005 - 2014 S-197 Mustang -General/Talk- 8
MrPerfect2 Engine 1991 - What does a normal idle suppose to sound like on OEM 5.0 ? Fox 5.0 Mustang Tech 7
horse sence Shaker assembly ,what year does it fit? 2005 - 2014 S-197 Mustang -General/Talk- 3
79 Fox Fox Burning oil... Does my theory make sense? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 9
79 Fox Fox Does this make sense? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
D Engine Does this look like TDC? (SOLVED) Fox 5.0 Mustang Tech 2
Blucifer99 Does anyone kno the deadtimes and voltage offset for these injectors Digital Self-tuning Forum 0
K Does Orange Dexcool Turn Red/Pinkish? S550 Mustang 2015+ (S550) Mustang -General/Talk 0
billison Does anyone else have one of these. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 15
BlakeusMaximus Where does antenna wire disconnect? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 1
B Does the coolant tank on this 4l v6 look ok? 2005 - 2014 S-197 Mustang -General/Talk- 0
DrSmart 95 GT Conv. Does the Keyless Entry Module feed power to the Speedometer? 1994 - 1995 Specific Tech 0
B 2001 gt Does it have a tune? SN95 4.6L Mustang Tech 1
R Engine Cammed 1988 Mustang LX - Does this sound right? Fox 5.0 Mustang Tech 11
Hudson N Anyone know what this does? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 7
M Interior and Upholstery What does this button do? 2015+ (S550) Mustang -General/Talk 2
R Does anyone know how to decode a 1970 Owner's card 1965 - 1973 Classic Mustangs -General/Talk- 5
jonnyb351 Stroker 4.6l 2v with a Vortech BE si supercharger won't start and missing when it does. 1996 - 2004 SN95 Mustang -General/Talk- 0
1995COBRA 95 Cobra starts right up and idles fine at first, but then after about 2 minutes, I try and restart and it does not hold an idle. 1994 - 1995 Specific Tech 12
J 1999 - What does this connector go to? SN95 4.6L Mustang Tech 6
7 Does anybody know what rims these are and what their worth 1965 - 1973 Classic Mustangs -General/Talk- 7
Similar threads