> Tech > Modifications > Mag-Hytec Diff Cover
Installing a Mag-Hytec Dana 80 Differential Cover
 Mag-Hytec Dana 80 Differential Cover 
Adds fluid capacity, easy oil changes, and a magnetic dipstick.


14718 Arminta Street
Van Nuys, CA 91402
(970) 879-4200


Geno's Garage
1150 Samples Industrial Drive
Cumming, GA 30041
(800) 886-2500

Visit Geno's Garage
for Truck accessories.
Geno's Garage Truck Accessories

       The Mag-Hytec differential cover increases axle fluid capacity and provides a magnetic dipstick to capture metal particles and simplify fluid level checking. Fluid changes are simplified because the Mag-Hytec cover uses a rubber o-ring in place of a gasket or bead of silicone RTV, and the cover features a drain plug.

Note: There are also installation instructions on the Mag-Hytec site.


Tools needed for installation:   

  • 14 mm or 9/16" wrench
  • 5/16" hex drive
  • Knife or thin screwdriver
  • Torque wrench
  • Flat file
  • Scraper

Supplies needed:

  • Shop rags
  • RTV gasket material or a two part epoxy
  • 8 Qts of gear oil
  • 2 bottles of limited slip additive (if you have the LS differential)

Installation Procedure (Total installation time is about 90 minutes + drying time):

Safety First! Park your vehicle on level ground and apply the parking brake.
Brake set? OK, you are ready to remove the cover Place a suitable drain pan under the diff cover. Use a 14mm or 9/16" wrench to loosen (for three turns) each of the 10 cover bolts.
gently separate the cover from the housing Use a thin blade to spread the cover from the differential housing. The OEM cover uses RTV sealer instead of a gasket, so you need to gently pry the cover loose to break the RTV seal. My favorite tool for this is a yard sale steak knife. I place the knife against the RTV seam and tap the knife into the joint with a hammer. When the seam separates, I run the knife around the lower part of the cover to loosen the cover from the housing.
drain the old oil Allow the old gear oil to drain from the housing before you remove the bolts and cover.
remove the cover clean all of the old oil out of the axle housing

Remove the cover and use a turkey baster, your finger, and rags to remove the old gear oil, sludge, and metal particles from the housing.

cover the internal parts and scrape the gasket residue from the housing Cover the ring gear and carrier with a rag, and scrape the remains of the old RTV from the housing mating surface. Try to keep dirt and old gasket material out of the gears!
seal all marks on the gasket surface On many Dana 80 housings, there are a couple of places where identification numbers were stamped into the mating surface. If the Mag-Hytec's o-ring seal hits these stampings, the seal may leak. Use a file to cut any raised edges from the numbers, then fill the divots with RTV, JB Weld, or some other impervious material. I used RTV to fill the numbers and several tool marks on my mating surface. Allow the filler to dry completely before installing the cover I let mine cure overnight, but you could start in the early morning, allow the filler to cure for 6 hours or so, and finish before dark.

Check the drain plug, oil reference plug, and 1/8 pipe plug for tightness. If you are going to install a temperature sender, remove the 1/8 pipe plug and install the sender in its place. Use an anti-sieze compound on the sender threads.

Using gear lube, apply a thin layer of oil to the Mag-Hytec cover O-ring.

install the cove and add 8 qts of oil

Position the cover by aligning the bolt holes and start one of the new stainless steel Allen cap screws and stainless steel washers at the top bolt hole and continue around the bolt pattern until all 10 bolts and washers are installed "finger tight." Using a torque wrench and a 5/16" hex drive, torque the cover bolts to 25 ft-lb in a cross pattern, and fill the differential with oil until the dipstick reads full (7 to 8 qts). Drive the truck for 20 miles or so and then check the level again.

Use a good synthetic gear oil for longer gear life under harsh conditions. I use Torco 75W-140 Synthetic Racing Gear Oil rated GL6. Others use synthetic gear oils from Amsoil, Redline, Lubrication Engineers, Royal Purple, and NEO. For normal use, a 75W-90 weight is fine. If you tow or load your truck heavily in hot weather, a synthetic 75W140 will provide better shear strength in the oil film for the heavily loaded gears. If you have a "limited slip" differential. Be sure to add to appropriate amount of friction modifier - it should take 2 or 3 bottles to provide enough additive for the extra oil capacity.

Refill capacity for the Dana 70 Mag-Hytec is 6 qts.
Refill capacity for the Dana 80 Mag-Hytec is 8 qts.

FWIW: The factory oil level is about 1/4 to 1/2 in. below the bottom of the axle tube. The min./max, marks on the Mag-Hytec dipstick correspond to the bottom of the axle tube (min.) and the bottom of the axle shaft (max.). The higher oil lever makes sure the bearings and seals our running in oil all the time. Bearings that run in oil run cool and clean themselves, and seals that run in oil last a lot longer. Mag-Hytec covers run about 45° cooler than the stock cover, and synthetic oil will run even cooler.

The Mag-Hytec Dana 70 cover will not interfere with the stock sway bar in the dodge trucks.
For the Dana 80 cover, 4X4 trucks do not have a clearance problem but 2WD trucks may require a space to clear the factory stabilizer (sway) bar. The folks at Mag-Hytec and any of their authorized suppliers know which trucks need spacers.

don't let your gear oil get like the stuff on the left! Next time, change the oil before the new oil in the jar on the right looks like the sludge in the jar on the left! Mine had 65,000 miles between changes, and that was too long. The Mag-Hytec cover will make this job easier to do the next time.


  Top of Page Home  

This page was edited on: May 3, 2004