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Mustang 7.5” & 8.8” Rear End & Axle Info

Posted 4/24/2009 by Jonathan McDonald

Ever wonder what rear end is in your Mustang or what is even supposed to be there in the first place? Use this handy Ford Mustang Rear Axle Info guide to learn more!

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If you own a 1979-2014 Mustang, then it came equipped with one of the two Ford rear ends – Ford 7.5 rear end or the Ford 8.8 rear end. All 79-85 Mustangs featured the 7.5” rear end. Starting in 1986 Ford introduced the popular 8.8” rear end in the Mustang. From 86-2010 the Ford 8.8” rear end went into all V8 Mustangs (5.0L, 4.6L and 5.4L) and the Ford 7.5” rear end went into all 4 cylinder (2.3L) and V6 Mustangs (3.8L). The 99-01 and the 03-04 Mustang SVT Cobras were equipped with an Independent Rear Suspension (IRS) what used the Ford 8.8” Differential. Starting in 2011, both the V6 (3.7L) and V8 (5.0L Coyote) Mustangs used the Ford 8.8” Rear End.

Ok so you know what Mustang rear axle assembly went into what years – now let’s look at what axles are in your Mustang rear end. All 79-04 Ford Mustang Rear Ends used 28 spline axles except for the 2001 and 03-04 SVT Cobras – they used a 31 spline axle in their IRS rear end. The 05-10 V6 Mustangs with 7.5” rear end used 28 spline rear axles whereas the 05-10 V8 Mustangs with 8.8” rear ends used 31 spline rear axles. For 2011-2014 Mustangs, both the V6 and 5.0L V8 Mustang were equipped with 31 spline axles.

Now that we got the what rear end you have and what Mustang axles are in your rear end cleared up - does this mean that your Mustang is still equipped with the Rear End that it had from Ford? NO! Many things could have transpired over the years to have let your Mustang end up with a Rear End it did not originally come with. Here are a few things to help you differentiate between a 7.5" & 8.8" Rear End.

The following information does not apply to IRS equipped Mustangs

Compare your Rear End Differential Gaskets to these pictures to start off with – 7.5” rear ends have two flat sides and two rounded sides where the 8.8” rear end has four flat sides:

If you are only working with a Rear Gear Set, here are a couple of things to check:

  • Measure the diameter of the ring gear. A 7.5" Ring Gear will measure 7.5". An 8.8" Ring Gear will measure 8.8".
  • You can also count the splines on the Pinion Gear. A 7.5" Pinion will have 28 splines & an 8.8" Pinion will have 30 splines.
With this new information you should be able to easily tell what rear end you have in your Mustang!

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Mustang 7.5” & 8.8” Rear End & Axle Info Tech Info

This Mustang Tech is designed to help answer questions about what rear end is in your Mustang and what axles you have in your Mustang's rear end. It covers the following year model Mustangs: Ford Mustang - 1979 (79) - 1980 (80) - 1981 (81) - 1982 (82) - 1983 (83) - 1984 (84) - 1985 (85) - 1986 (86) - 1987 (87) - 1988 (88) - 1989 (89) - 1990 (90) - 1991 (91) - 1992 (92) - 1993 (93) - 1994 (94) - 1995 (95) - 1996 (96) - 1997 (97) - 1998 (98) - 1999 (99) - 2000 (00) - 2001 (01) - 2002 (02) - 2003 (03) - 2004 (04) - 2005 (05) - 2006 (06) - 2007 (07) - 2008 (08) - 2009 (09) - 2010 (10) - 2011 (11) - 2012 (12) - 2013 (13) - 2014 (14)