GTPetros

My 07 Gt has a diff that’s going bad and after seeing how much of a pita it is to replace the ring and pinion I figured it’d be easier to just swap the whole rear axle assembly with a differential that has a gear ratio of my choice (3.73) as well as an lsd and I can do the suspension and brake modifications along with the install. After doing some digging it seems like ford used the same 8.8” 31 tooth spline that my car has from factory across a bunch of other models that might be compatible with mine. Best case scenario would be a 3.73 with an lsd and disc brakes off the bat. Any advice or personal experience/knowledge would be appreciated thanks

05stangkc

My Best Advice is Using an 05-09 Mustang GT Rear Axle. 3.55 Will Be a Lot Easier To Find Than 3.73 Unless You Can Find a Wrecked Gt-500 Kr. I Had 3.55's in My 07 GT/Cs and They Were Plenty Low Enough! Find a Clean Low Mile if You Can.

Here are The LKQ Listings!

https://www.lkqonline.com/2009-ford-...r/-hXDDmmncOPD

Bert

agreed -- an axle from any 05-09 GT should work (10-14 also?) and, assuming your car is a manual, 3.55 seems like the best compromise on ratio to me. I originally had 3.31 which was a little too tall; went to 3.73 which seems a little too short in most situations; 3.55 would be "just right"

05stangkc

I Completely Forgot About The Gen II S-197's! If You Search 2011,2012,2013 & 2014 You Get Some 3.73 Options as Well As The Torsen Diff To Boot! I'm Not 100% But it Sure Has To Be Real Close if Not Bolt on. Rear Brakes May or May Not Be a Factor as Well.


https://www.lkqonline.com/2013-ford-...r/-hGKFmnncOPD

m05fastbackGT

For N/A applications, 3:73 are the sweet spots... If you're running forced induction or nitrous, I wouldn't recommend anything beyond 3:55 for street/highway usage... You can purchase both 3:55 and 3:73 ring gear and pinion sets directly from Ford Performance Parts... Attachment links are provide below, if interested?

https://performanceparts.ford.com/part/M-4209-88373
https://performanceparts.ford.com/part/M-4209-88355

m05fastbackGT

As for rear axle swaps? If you can locate one with 3:73, I would recommend it, providing your N/A... If you're not able to locate an axle with 3:73 then locating an axle housing with 3:55 would be you're next best option for both N/A and forced induction applications.