FORD STERLING - F 12-10.25 & F 12-10.5
Please read entirely before installing this new differential cover.
1/2 socket wrench and driver (for removing the old cover)
1/4 allen bit with a 3/8 ratchet drive (1/4 allen key is furnished)
3/16 allen bit with a 3/8 ratchet drive (3/16 allen key is furnished)
3/8 drive torque wrench
Smooth flat file by 8 to 12 in. long
Oil drain pan (minimum 8 Qt. capacity)
New gear lube API Spec. GL-5, MT-1 ("LE" 607 for severe service and extreme HD applications
and temperatures of -20 to 230 deg. F). ("LE 9920 75-140 Synthetic") for warranty reasons and
extreme low and high temperatures of -50 to 280 deg. F). The Stuart Friction Modifier bottled by
Torco Co. (for "limited slip" differentials only) 4 oz. per 3 qt’s. of gear oil. The "LE" Gear Oil and
the Friction Modifier can be purchased at Mag-Hytec.
Number Quantity Item
1. 1 Mag-Hytec Differential cover with O-ring ARP 568-277 (installed)
2. 12 5/16-18 stainless allen cap screws (Torque 12-16 ft. lbs)
3. 14 5/16 stainless AN washers
4. 1 Drain plug assembly with magnet and O-ring ARP 568-910 (installed)
5. 1 Dipstick assembly with magnet and O-ring ARP 568-910 (installed)
6. 1 Oil level reference plug with O-ring ARP 586-904 (installed)
7. 1 1/8 pipe plug (for optional temperature sender not included)
Dipstick, Drain plug, Reference plug and 1/8 pipe plug (Torque to 30 in. lbs)
A word of caution to the installer / vehicle owner:
The Mag-Hytec cover is designed to fit the factory Ford Sterling axles as supplied as original equipment. However, in some
applications, or because of the use of certain factory options and/or after market equipment, there may be clearance problems between
your Mag-Hytec cover and other vehicle systems (specifically some rear sway bars). It may be necessary to install spacers or shims to
lower the sway bar. It is the responsibility of the vehicle owner/cover installer to ensure that no other vehicle component comes in
contact with the Mag-Hytec cover. Contact with any vehicle component, or the making of any modification to the Mag-Hytec
cover, automatically voids the warranty. Mag-Hytec assumes no liability, expressed or implied, for damage or injury to persons
FORD # F 12-10.25 & # F 12-10.5
Note: For some installations, removing the spare tire may provide better access to the work area. However, it is not necessary in every
case. The installer should determine if there is adequate work space prior to starting the installation.
1. Park your vehicle on level ground and apply the parking brake.
2. Position a drain pan under the differential to catch the old gear lube.
3. Remove the 12 existing bolts, starting at the bottom.
4. Using a gasket scraper, start at the bottom of the cover and carefully (so as not to gouge the housing metal) insert between the
existing cover and gear housing and pry the old cover off.
5. Allow all of the old gear lube to drain.
6. Using a gasket scraper, carefully remove all of the old gasket material (dried silicone) from the housing.
7. Use clean lint free rags to wipe down the remaining oil from inside the housing and to clean the housing gasket surface. The
surface must be clean and flat for the Mag-Hytec’s O-ring to seal.
8. Before installing the new Mag-Hytec cover, check the gasket matting surface on the differential housing for dents, irregularities, or
gouges. Should any exist, carefully remove the high spots using a smooth flat file. BE CAREFUL NOT TO “ROUND OFF”
THE FLAT GASKET SURFACE.
9. Using gear lube, apply a thin layer of oil to the Mag-Hytec cover O-ring.
10. 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 12 bolts and washers are installed “finger tight.”
11. Using a 1/4 hex bit and 3/8 drive torque wrench, torque the stainless allen cap screws to (16 ft. lbs.) in a “cross tight” pattern.
12. Check the drain plug, oil reference plug, and 1/8 pipe plug for tightness. If you are going to install a temperature sender, do so at
this time. Remove the 1/8 pipe plug and install the sender in its place. Be Sure To Use LPS All Purpose Anti-Seize or equal On
The Sender's Pipe Threads. "TIGHTEN" all three: DRAIN PLUG, OIL REFERENCE PLUG and 1/8 PIPE PLUG TO
(30 in. lbs) DO NOT OVER TIGHTEN.
13. Remove the dipstick assembly and add in the new gear lube. Your new cover will take approximately 6 qt’s. to fill ( to bottom of
axle ) for the Ford Sterling 12-10.25 & 12-10.5. There are two marks on your dipstick. The bottom mark represents the
minimum fill line and the top mark is the maximum fill line. YOUR OIL LEVEL SHOULD BE BETWEEN THESE LINES.
Note: when checking the oil level, remember to thread the dipstick assembly in by hand until it is snug against the O-ring.
Remove the dipstick assembly and check the level. If the oil level is at the full line, apply a thin film of oil to the dipstick
assembly O-ring and reinstall. Tighten snugly to (30 in. lbs). DO NOT OVER TIGHTEN THE ASSEMBLY.
Drive at least 25 miles and check oil level. If you have a special application vehicle, or your vehicle has been modified or “lifted”
and the axle has been rotated, you will have to establish the correct oil level for your vehicle as the dipstick marks as supplied by
Mag-Hytec will not apply. The high oil level is the top line on the Dipstick (The bottom of the axle). The low
oil level is the bottom line on the dipstick (the bottom inside of the axle tube). Once you have established the
correct level, scribe a reference line on your dipstick for future reference and fill the differential.
14. If you have a “limited slip ”differential, be sure to add the appropriate amount of friction modifier. We have
had excellent results with the Stuart Friction Modifier product sold under many private labels can be purchased at Dodge, Ford, or
Mag-Hytec and it is compatible with the "LE" and Amsoil gear lubes. One 4 oz. bottle per 3 qt’s. of gear oil (TWO 4 OZ.
CONTAINERS SHOULD PROVIDE THE DESIRED RESULTS).
A forum community dedicated to Diesel engine owners and enthusiasts. Come join the discussion about performance, builds, ecodiesel, towing capacity, modifications, classifieds, troubleshooting, maintenance, and more!