Moser 12 Bolt and 9 Inch F Body Installation Instructions



Special thanks goes to Grifter on LS1tech for letting me use his installation pictures.  Moser includes some excellent instructions with their rear ends, but the pictures below along with some additional information may help you out.

The Moser housing comes shipped in a large box that can be seen in the bed of this pick up truck.  The axles are shipped in another box, which can be seen hanging over the tailgate.  The center section comes in a plastic case, shown ahead of the box the axles are in.  The torque arm bracket, bearings, instructions, etc, are in the small box on the tailgate.

Here's the specs on Grifter's rear:
Moser 9 inch
35 spline axles
4:10 gears
Lower control arm relocation brackets
Swaybar brackets

Grifter painted the housing and center section using POR-15.  The Moser housing comes unpainted, although Moser offers a powdercoating option.

Grifter cleaned the housing and center section using a wire brush, 100 grit sandpaper and solvent.


Here is what the parts look like after the first coat.


Now it's time to take out the old 10 bolt rear.


The 35 spline axles are quite a bit larger in diameter than the stock axles.


The brake backing plates need to be reused from your 10 bolt rear.  This means that the axles have to be pulled out, and the wheel bearings removed, to slip the backing plates off. The 10 bolt axles are held in with c clips.  Sometimes you have to push in on the axles to get the c clips to pull out.

The backing plates go on, then the bearings get pressed on.  Note: The nine inch axles are not the same length for the driver side and passenger side.  The PASSENGER (RIGHT) side axle is the LONGER axle, driver side being the shorter axle.  You need to make sure you get the backing plates on the correct axles before pressing the axle bearings on. The above picture shows one axle (left side of pic) with the bearing pressed on.  The other axle has yet to have the bearing pressed on.

The picture above shows the bearing getting pressed on.  A lot of Napas and small machine shops will have a bearing press and charge a small fee to press the bearings on.

Moser supplied studs are installed in the housing around the perimeter of the center section hole. These fasteners need to be drawn through the housing. Don't attempt to install a nut on the stud to draw it through, if the threads are only protruding through a few threads as they are in the above picture. Damage to the studs and nuts can happen, and we recommend using a c clamp to draw the stud partially though, further than the above picture shows. You can draw the stud through the housing using a c clamp by placing an oversize nut on the housing where the stud hole is, enabling the stud to draw through the oversize nut. 

Prior to installing the center section, make sure to clean any debris out of the inside of the rear.  We normally clean the rear out with brake cleaner and then blow it dry with compressed air.  Moser supplied studs are then installed in the housing around the perimeter of the center section hole. The Moser supplied gasket is installed and the Moser pre-assembled center section is slipped on.  Moser supplied washers and nuts are then installed and torqued to 45-50 ft lbs..  Note that it is common to have to use a rubber mallet to gently tap the center section down over the studs.  We RTV the base of the studs where the nut/washer will press down, to prevent any leakage out of the studs.  Prior to installing the (inner housing seal) axle seals, RTV' all around the inside where they are going to get tapped in.  Once the seals are tapped in, use your finger to apply RTV around the edge of the seal.



Moser 7S151 - Inner Housing Seal (1.531")


Moser Engineering Inner Housing Seal. Designed to be used with 1.531" & 1.562" Ball Bearings.
The Inner Housing Seal installs flat side facing you and is driven into the housing end until it seats.

Timken Wheel Bearings

If you have ordered a Moser rear with Timken wheel bearings, do not use the inner wheel seals. The Timken wheel bearings need to be lubricated and the inner seals prevent the bearings from getting the necessary lubricant.


Note: The 1/8" shims are for using LT1 brakes


Note: It is quite common for the wheel bearings to not have an o ring. In this case you simply use silicone sealer (RTV) around the outer edge of them prior to installing the axles into the housing.


The torque arm bracket bolts (3/4x16 - 3.25 long") to the three bosses on the rear end.


Make sure you do not install the upper torque arm to bracket bolt as shown in the picture. The bolt needs to be turned around for adequate clearance with the chassis floor.

Shown is a rear with the four channel ABS/TCS. The exciter ring can be see next to the brake backing plate. The emergency brake shoe has been removed in this photo, which is necessary to gain access to the four bolts that secure the brake backing plates. The 9/16 Craftsman wrench shown was ground down to make it thinner around twenty five years ago. Even though the wrench has been made thinner, it is still strong. It was used to install hundreds of (PTO's) power take off units on trucks over the years, and works very well on these nine inch Moser rears.

You can cut off half of the e-brake bracket on each side so only outer half (part with cable and brake line) is bolted to brackets.


The axles are now installed as well as the brake calipers, rotors, etc. 
Note in the picture below that Grifter has the lower control arms in the middle set of holes, on the Moser supplied lower control arms.  We have found with most of these cars that more traction can be found by using the bottom set of holes, for the lower control arms.



Gear Lube Fill Location

The gear lube fill is located on the left side of the housing on the Moser 9 inch rear end.  It is relatively close to the torque arm bracket.  Fill the rear up until the fluid starts to seep back out of the fill hole.  It should only take three quarts of gear lube. The gear lube fill plug takes a 3/8 allen head wrench to remove and install it. If you ordered your rear with the optional fill located on the back of the housing, you still have to remove the fill plug on the side of the housing, as the gear lube level needs to be at the bottom of the side plug hole when full. Don't fill the rear to the bottom of the rear fill hole, it will have to much gear lube in it. Too much gear lube can cause a leak at the ends of the housing.


You will need several feet of vacuum tubing to connect to the vent, located on top of the driver side axle tube.

The factory and most aftermarket torque arms will bolt up to the Moser torque arm bracket.  Sometimes it takes a little grinding on the end of the torque arms to get them to fit.  Fit the torque arm to the rear to make sure it fits before the rear is bolted up into the car.  Factory and aftermarket panhard bars and lower control arms will all bolt up without any problems.


The factory driveshaft can be reused but a conversion u joint will need to be installed.  Napa pn 447 is the one we have always used.  Keep in mind the factory driveshaft isn't much stronger than the 10 bolt rear.  It can turn into a pretzel under the car, taking out the exhaust system and puncturing the floorboard.  The driveshaft should also be an inch longer when used with the Moser nine inch, although a lot of people have gotten by with the stock driveshaft.  I have seen twice where the stock length driveshaft caused a vibration that was resolved by going to a one inch longer driveshaft.  I have sold and used the PST 3.50 aluminum driveshafts for years, and they have handled all the punishment my Camaro threw at them.

The standard Moser 9 inch weighs approx 50lbs more than the 10 bolt.
The Moser fabricated 9 inch (M9) weighs about the same as the 10 bolt



                   How tight should I tighten my u-bolts?

1310 series and 1330 series should be tightened to 17 ft/lbs and 1350 series to 20 ft/lbs. You should never tighten the nuts on any u-bolt excessively. This will cause the cap to distort and the u-joint will fail prematurely.


Heavier Duty Pinion Seal

CR-547785 uses Viton instead of natural rubber ($8.50 each). The fit is the same although the seal design is a little more robust. They ship these seals for multiple end uses including NASCAR. This seal should eliminate any pinion seal leaks.


1998 to 2002 F Body  3 Channel ABS:

The uncoated wire needs to be cut off its not used, then just connect the other two it doesn’t matter what wire goes to what wire. It just makes a loop inside of magnetic pickup. There is no wrong way to hook up the two wires. 


Moser 12 Bolt and 9 Inch F Body Installation Instructions
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  • Item #: Moser Installation Instructions
  • Manufacturer: Moser Engineering
  • Condition: New
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Price $99,999,999.00

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