Project Dodge Ram Mega Cab: AAM 11.5 Differential Performance

Oct. 20, 2010 By Jaime Hernandez
Our Dodge Ram’s rear needed some attention, including performance upgrades for towing/hauling and bigger tires.

If your truck is pushing big off-road tires or doing any serious hauling and towing, it’s time to upgrade your rear axle with a high oil capacity differential cover. This easy upgrade can be done in under one hour and will add performance and great looks to your truck’s rear end.

We decided to work with Oasis Differential Covers (ODC) ( out of Anaheim, California, because they use low-pressure casting technology on their aluminum differential covers. They also offer some unique designs that are bold and add function.

Black Oasis diff cover with machined fins for American Axle (AAM) 14 bolt 11.5 inch rear axle.  This will fit 2003 – 2011 Dodge Ram 2500/3500 trucks (Part# ODC05-GB).

Here are some of the features of the Oasis Differential Cover:

• Heavy-duty construction
• Low-pressure aircraft-grade aluminum casting, which is superior to die and sand casting
• Wrinkle powdercoat finish
• Larger oil capacity for increased lubrication (an honest 1 L on our Dodge Ram 2500)
• SS magnet drain plug traps any metallic debris
• Separate fill and drain plugs for easy oil changes without removing the cover
• Stainless-steel bolts for a maintenance-free finish
• 100% American made


We took a wire wheel and brush to get rid of some of the caked on dirt and surface rust. Then we rattled some industrial black paint on the axle housing to bring it up to snuff.  We felt it was necessary to do this to welcome our new Oasis diff cover.

The installation is pretty straightforward. You’ll need the following:

• Socket Wrench
• 1/2 SAE socket
• SAE Allen socket set
• Torque wrench
• Oil drain pan with open top
• 5 Liters of SAE 75 W – 140 Lucas Synthetic gear oil
• Gloves
• Eye protection
• Black RTV (provided by Oasis)
• Wire brush (optional)
• Black spray paint (optional)

Step-by-step instructions are provided by Oasis Differential Covers. The only thing you need to research is what type of oil your diff uses and the torque spec to tighten the diff cover bolts.

On our Dodge Mega Cab, the rear diff cover removal from the AAM 11.5 inch was as easy as removing a total of 14, 5/8 bolts. When doing this, make sure to have your oil drain container in place, and remove bolts from the bottom up. Leave a few of the top ones in place to allow you to control the flow of oil coming out of the rear diff. You may need to slightly pry the bottom part of the diff cover to allow oil to escape the housing.

After all the oil is out, remove the old diff cover. Using a clean rag, try to get as much of the remaining oil inside the bottom of the diff housing out.

Using a gasket scraper, clean the surface from any dried silicone or gasket material. This will help ensure a good, flat surface to mount your new Oasis diff cover to.

Side by side, the difference in size and depth is pretty obvious (Oasis on left, Factory AAM on right).

Adding some Black RTV provided by Oasis to differential cover. The RTV should run around the bolt holes.
Stainless steel bolts provide by Oasis to ensure a clean installation.

The big question at this junction is whether to use thread locker. It’s a preference. 

From the factory the AAM comes with a red thread locker, but it’s not for certain if it actually is the heavy-duty red. 

If you plan on disassembling the diff cover in the future, the medium-duty blue thread locker or nothing at all is a better option. 

Torque spec for the AAM 11.5 diff cover bolts is 24 ft/lb.  Tighten the bolts using a cross pattern to ensure equal surface pressure on diff cover.

Since we go off-road frequently on rough roads, we opted to use the red stuff.  Keeping our hardware tight is important. The only downside to using the heavy-duty red thread locker is that if we ever need to take the bolts off, we will need to heat them up to break the lock.

We used Lucas SAE 75W – 140 synthetic gear oil as part of our diff cover upgrade. Lucas Oil is trusted by some of the top off-road racers like Carl Renezeder and professional truck drivers across the Interstate.

Lucas Oil contains special synthesized additives that insure less gear rattle, less whine and longer bearing life. It also works well with limited-slip differentials. We had used it on many other vehicles, ranging from a 1967 Nova to our trusty Chevy Z71.

We really like it, and it’s made in the USA.

To make sure we didn’t make a mess, we used a small piece of plastic hose to get the oil into the diff cover fill hole. You can also buy a fill hose from your local auto parts store that will screw right onto the bottle.

We were excited to be able and get an extra 1 L of Lucas Synthetic Gear Oil into our new Oasis diff cover. Extra oil means extra lubrication. 

After completing the fill, we put on the fill plug and tightened it up, checked for oil leaks, and cleaned up our work area.

Make sure to recycle your old gear oil at your local auto parts store when done.


So far we have logged over 800 miles with our Oasis Diff Cover and Lucas Oil. No leaks, still looking great and the Lucas Oil is as clean as it was when we first put it in.

The Oasis diff cover has good clearance, so we haven’t had any problems hitting rocks off-road.  Dirt comes off easily; just use some soap and water with a few strokes of a plastic brush--done.

The aluminum fins on the Oasis diff cover help get rid of heat a lot faster than the stock metal cover on the truck. We also have gained gear oil capacity of 1.2 Liters over stock, for a total of 4.8 L. That’s almost a 20% increase in lubrication. This should really help our rear end when towing or working hard on and off-road.

Overall, we’re really happy with our Oasis diff cover. Not only does it look great, it’s also helping our hard working Dodge Mega Cab keep its tail cool.


Oasis Differential Covers

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