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The Torsen differential available on later Mustang 5.0s was not available in 2011. Instead, this Project Mustang is equipped with Ford’s “Trac-Lok” differential. The Trac-Lok is a clutch-type limited slip differential with great street manners, launching ability, and corner-carving characteristics. It’s a Jack of All Trades and a master of none. Unfortunately, in autocross and road racing, the use of wide, sticky tires and applying power out of corners causes the Trac-Lok to use those clutches a lot. The clutches operate on friction. Friction creates heat, and heat melts clutches. To prolong the life of my Trac-Lok until I could afford a stouter differential, I needed some sort of cooler. While an active differential cooler with a pump and heat exchanger would have been totally trick, the cost of that would be more than upgrading the differential itself! Fortunately, Ford Racing had a solution.
Ford Racing’s aluminum differential “heat sink.” You can see how big the fins are for increased cooling surface area. The two drain/fill plugs are also a nice touch, because differential fluid with friction modifier is nasty.This is an aluminum differential cover that replaces the stock stamped steel piece. Aluminum conducts heat better than steel, and all those fins increase the surface area, which allows even more heat to be conducted out of the differential. Ford Racing claims a 10 degree temperature decrease in open track racing just from installing this new diff cover. Since the Grey Project Mustang is mainly autocrossed for less than 90 seconds at a time, this should equate to much lower differential fluid temperatures since the heat sink will help cool the fluid off much more between runs. As an added bonus, there are drain and fill plugs on the new cover, which allow draining and replacing the fluid without taking the entire cover off (which can get very messy). Those plugs can also be used for temperature senders or an active diff cooler.
The cooling fins extend into the fluid reservoir to increase the surface area and thus heat transfer there, as well.
The differential cover comes as a kit from Latemodel Restoration. LMR includes ARP fasteners, because everyone likes ARP stuff.
Here's the “Passive Differential Cooler” installed. I’ll save you the boring details of the installation, because nothing has changed when it comes to swapping Ford 8.8” differential covers in the past three decades. It’s a very pretty piece once installed, though.There is little way to quantify how effective this diff heat sink is working; doing so would require a temperature probe and some sort of before/after test. However, Project Mustang's Trac-Lok is still functioning quite well, even after three hard seasons of autocross.
The final part added to the grey Project Mustang is a tool everyone who drives their vehicles hard should have at their disposal: a good set of gauges. Gauges allow you to see if you’re pushing your vehicle too hard by monitoring critical vehicle parameters and letting you back off before you could permanently damage something. Factory gauges today are notoriously inaccurate. Instead of showing meaningful data, they are now just glorified idiot lights. The widely-held belief is that manufacturers reduced the sweep and resolution of their gauges to prevent customers from coming in and saying “OMG, my oil pressure gauge moved!” The result is that now most of your factory gauges won’t tell you anything is wrong until it’s too late.
