Project Grey Mustang 5.0: Part 5 – Putting the Power Down with Eaton


After having performed this extensive research, I ordered a TrueTrac from Eaton and drove over to Justin’s Performance Center near Baltimore to have it installed.  JPC is a national authority in all things Mustang, and they’ve installed so many LSD units in Ford 8.8” rears that they can perform the procedure in their sleep.  Furthermore, they are absolute perfectionists who carefully inspect every single part they touch. 


Project Mustang gets ready to have its LSD swapped.

Installing a differential is an involved process.  Pretty much the entire rear end needs to be disassembled: the wheels and brakes need to be removed so the axles can be slid out of the tubes.  Reinstalling the new differential requires installing shims to get everything spaced right, a process that requires as much patience as it does skill.  I don’t have patience, so I leave this job to the professionals.


Here is one of the two axles pulled out.  The splines in the top are what slide into each side of the limited slip unit.


Everything removed except for the pinion gear.  You can see where the bearings and races sit on either side of the differential housing.
Old and busted Trac-Lok.  You can see the ring gear uninstalled behind it and the bearing retainer cap to the right.  That S-shaped… thing in the center is actually the spring that presses on the clutches.

While they were installing the new differential, Aaron at JPC recommended changing out several parts that were in there, as they were maintenance items and simple to do while everything was apart.  Since Project Mustang 5.0 is getting close to 40K miles, I figured it would be a good idea.  JPC handled the Ford Racing Ring Gear and Pinion install kit, which included upgraded high-torque bearings and races.  I also had them replace the axle seals at each end, because they’re only $11 apiece.

Unfortunately, in my eagerness to drive Project Mustang with its shiny new parts installed, I neglected to take a picture of the new differential installed.

One advantage of the Eaton TrueTrac is that it doesn’t require synthetic lubricants or friction modifiers.  (In fact, Eaton “strongly recommends” non-synthetic oil and NO friction modifier.  They say the TrueTrac was designed for dino oil, and that synthetic lubricants and friction modifiers can actually decrease the bias ratio.)   This is an added bonus, since I now no longer need to spend $70 on three quarts of full synthetic 75W-90 and a bottle of Ford Friction modifier.  Lucas Oil still makes a high-quality non-synthetic gear lube, so I had JPC fill up the diff housing with three quarts of Lucas Heavy-duty 80W-90, the viscosity specifically recommended by Eaton.

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