mustang gt rear end/differential rebuild cost vs doing it myself


Oct 28, 2020
Hello, the rear differential on my car seems to be bad. Mechanic said there is a 1/4" or 1/2" play (cant remember properly) when he moves the driveshaft and the best quote I had was $1600 for rebuild. I need to decide whether to have a shop do it or do it myself.

If I do it myself then I am thinking of getting a new carrier with spider gears installed here ($350):

or I can get a used one like this:

I will need a shop to press the races on with the bearings. A yukon bearing kit including shims is for about $85 on ebay.

A backlash gauge is about $90 and a ford racing 3.73 pinion/ring gear is about $170 on ebay. A used 3.27 set is about $115 on ebay.

A gasket is about $12.

I could try to rebuild the differential using all these parts without taking out the old one in case I can't do it or mess it up. If it goes well then I can just replace the rebuilt differential with the old one right? Am I thinking this too simplistically or am I being realistic? What am I missing? That is about $450-700 to do it myself plus whatever a shop will charge me to press the bearings/races if needed. I will mark everything else with a punch or paint so that I can put it in the same way it came out.

The thing I am concerned with is properly putting the c-clips back on as that is the only thing holding the axle shafts in. Is there a way to verify I have done it properly? Also what is the difference between 31 and 28 splines? What part is this referring to? Are they interchangeable? My car is a 2000 mustang gt with manual transmission, what will the stock/factory splines and gears be on this car? I think the stock are 3.27 gears from my other thread. Also I bet there is all the metal shavings going around, will they have damaged anything else like the housing? It might be better to keep everything stock for my use.

Thank you for your help.
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5 Year Member
Apr 16, 2015
First off, what kind of play? Rotational or up and down movement at pinion? If rotational, was it play in the rear end or driveshaft (could be u-joints).

Removing and installing the c-clips is probably one of the easier aspects of the rear end build. Not hard putting them in.


Active Member
Feb 19, 2018
You should watch or download the instructions for this. Some notes, a 7.5 or 8.8 axle will have up to an eight of an inch of in and out movement on the axle shafts when installed. Not a issue. If you have a quarter inch of backlash, that is excessive. That means if you hold the pinion still and the ring gear can rotate a quarter inch, you have some wear.

Suggest buy some oil and posi additive and pull the rear cover to check what is worn. It could be the ring and pinion, or the spider gears. Its worth looking before you spend money. C Clips are easy, getting the pinion cross pin lock bolt out can be a prob if it breaks. Getting the carrier back in with the shims on the side can also be a pita. Done several at home. And torquing the pinion nut to 300 ft lbs to set the crush sleeve takes some finagaling.

I recommend taking the rear out of the car to work on. It may take a few days to get through it the first time.
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