F150: Installing a Mag-Hytec Differential Cover

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By Michael Zimmers
30 July 2004

My 2001 F-150 has seen mostly tame street use in its first 49,000 miles, but a planned trip into the Sierra Nevada mountains during the end of summer was going to change this. Envisioning very high air temperatures, steep hills and other challenges to keeping a drivetrain cool, I decided to install a finned aluminum differential cover.

After poking around online for alternatives, I settled on the Mag-Hytec cover, for a few reasons:

  • I liked the pictures of the product on their website, www.mag-hytec.com
  • I was impressed by the detail about the product and installation on their site. It was evident that a lot of forethought went into the design and delivery of their products.
  • The price was reasonable, as were the shipping costs
  • When I called their number, the person who answered was friendly, informative and patient. I’m a sucker for good customer service and theirs was excellent.

The cover and the fluids arrived two days after ordering and were well packaged. When I unpacked the cover, my positive feelings about my choice were reinforced: the Mag-Hytec cover is very well made. The cast aluminum is thick and has a good feel to it, the powder finish is excellent and the included installation hardware is of high quality.

Here’s a view of the inside of the Mag-Hytec cover. One feature worthy of note is the dipstick, which allows you to measure fill a bit more accurately than just sticking your finger into the fill hole. Also notable is the rubber beading which is inserted into a channel on the mating face of the cover. This beading eliminates the need for any brush-on gasket material.
This is a view of the original differential cover. (I took this picture before I decided to remove the spare for better photo-taking.) If you look closely, you can see that the paint is missing from almost the entire upper half. I was told that this is the area above the fill line, and the paint being gone is evidence that the diff was indeed running fairly hot.
After putting a drain pan underneath, I broke loose the 12 bolts holding the cover in place I then removed them all but one at the top, which I loosened about three full turns.

Because the factory used a gasket sealant, I had to pry the cover loose. I used a putty knife for this, to minimize any chance of dinging up the mating surface. Once it came loose, the gear oil drained out. Keeping the cover partially on prevents the fluid from going anwhere but straight down. Once drained, I removed the final bolt and the cover.

In this picture, I tried to show the gasket cement that needs to be completely removed from the mating surface. The dark area under the gear teeth is the material that must be removed. I used a putty knife, and then a razor scraper…
…and finally some #0000 steel wool (#000 would probably have been fine, too, but I had #0000 on hand). Use of steel wool or any abrasive will generate small particulate matter that is best kept out of the machinery, so before using it, I covered the innards of the differential with a shop rag.

When the mating surface is free of all gasket material, it will be lightly rough to the touch, due to the machining scores on it.

After cleaning the mating surface thoroughly, it’s time to wipe off any excess oil from the inside of the differential. It’s best to use a cloth rag that won’t snag or throw any lint. The bottom of the differential also holds a few ounces of oil that won’t drain, so I reached in with a wad of paper towels and sopped this up.

The installation instructions also advise to look for any irregularities in the mating surface, and to carefully remove them with a file. Fortunately, my differential was in good shape, so I didn’t have to perform this rather delicate step.

Before installing the Mag-Hytec cover, I smeared a little gear oil on the mating surface, being sure to cover the rubber beading.

Using one of the new bolts supplied with the cover as a pilot, I matched up the bolt holes and installed all of the other bolts finger-tight. I then torqued them down to a very light 16 ft-lbs, using an alternating pattern. The instructions emphatically state not to over-tighten, and this seems like good advice to follow.

Once the cover was tightened down, I double-checked the tightness of the drain plug (which is only to be tightened to 30 INCH-lbs) and filled the differential. First came a couple of bottles of friction modifier for the LSD, then the Almasol gear oil recommended by Mag-Hytec.

As I had removed the spare, there was plenty of room to use a funnel; had I left the spare on, a lube pump might have been necessary.

Although Mag-Hytec told me I’d need 5 quarts of gear oil, my level came above the "low" indicator after 4 quarts. (The yellow arrows denote the "low" and "high" scorings on the dipstick; the red arrow is where my oil level read after 4 quarts.) I’ll drive it for a few days and recheck.

The entire installation took less than 90 minutes, including unpacking, clean-up and time-outs for photography. This project has piqued my curiosity about fluid temperatures, so I may well add a temperature guage (the Mag-Hytec cover has a hole pre-drilled for a sender unit) from www.egauges.com. I’m also planning on installing a Mag-Hytec transmission cover as well, based on my positive experiences with this effort.

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