When it comes to product development, we only make products that increase performance and beat the competition. So when we tested the popular Diff Covers on the market, we were shocked to find out that they actually hurt performance. This lead to the development of something so New and Incredible that our performance design has a United States Patent. Look, when we set out to build a product for your vehicle, we only engineer the best. What else would you expect from a company with a winning legacy that spans decades. We are here to win, and we just did (AGAIN) in a huge way.
US Patent #10,443,705
The Banks Engineering team’s goal was to perfect fluid flow and reject BTUs from the fluid as fast the ring and pinion puts them in. If the fluid flow is impeded in any way, it results in resistance and aeration which reduce fuel economy and creates heat, thereby degrading the fluid and decreasing the lifespan of the gearset.
Almost all aftermarket covers have fins for cooling. Unfortunately, those fins are almost useless because there’s little or no airflow immediately behind the differential. Nearly all aftermarket covers impede fluid flow. Why does this matter? Aim a fire hose at a brick wall. It turns out liquid doesn’t like 90° angles or obstructions.
Die-Cast Aluminum Construction
A380 aircraft aluminum die-cast for exceptional strength and precise fit.
12-point chrome-plated flanged mounting bolts.
Class-Leading Heat Rejection
24 external radiator fins offer 534 square inches of surface area to ensure optimal heat rejection.
Patented Ram-Air Scoops
Ram-Air system directs cool high-velocity air through radiator fins, eliminating the dead zone. Designed with breakaway scoops.
Magnetic Fill Plug
Magnetic fill plug. 20° angle for easy fill. Simplifies oil changes.
Sight-Glass with Contrast Screen
Sight-glass with contrast screen and Viton O-ring seal.
Magnetic Drain Plug
Recessed magnetic drain plug. Simplifies oil changes.
Radiused ports for smoother fluid flow.
Directional Fluid Guides
Axle-tube guides direct fluid to axle bearings without churn.
Integrated No Mess Viton Seal. Dry-mount silicon high-pressure O-ring seal. No messy RTV required.
Precision Fit Machined Surface
CNC-machined surface ensures precise fit.
Internal Heat Absorption Fins
Internal absorber fins offer 120 square inches of surface area to transfer heat to external radiator fins without disrupting fluid flow.
Simple Fluid Change
No need to remove cover to change fluid.
Ring gear raceway provides path for fluid flow to pinion and ring gear-bearing sets.
Ram-Air System w/Breakaway Scoops
Ram-air scoop break away point prevents damage if scoop is snagged.
What began with a simple question, resulted in millions of video views, innovation and another patented Banks product.
More than a year ago Gale questioned the benefits of aftermarket diff covers asking, "Are they just bling or are they really doing something?" The answer wasn't as easy to uncover as he'd hoped. Out of dozens of manufacturers, only one claimed to reduce fluid temps, yet no data could be found to back up those numbers. All other manufacturers, and there are many, simply copied the originator's design. Manufacturers still parrot the same phrase today, "More oil means cooler temps." Although there's some truth to it, what Gale and the Banks Engineering Team uncovered were two underlying problems with aftermarket covers; poor air flow and flawed fluid dynamics. The Banks Ram-Air differential cover solves both issues.
After testing covers with flat-backs and those with larger fluid capacities, it was apparent that these covers do not cool as well as advertised and suffer from poor fluid dynamics. As a result, they reduce fuel economy. With its computer-aided and road-tested design, the Banks Ram-Air differential cover retains fuel economy and extends lubrication life!
Many have asked, “Why did testing take so long?” Well, there was no precedent for testing rear differential covers, nor was any data available for rear differential lubricants as tested in vehicles. “There are just too many variables,” said the lubricant companies. Creating the proper test procedures was incredibly time-consuming. We started from scratch several times. We even burned up our chassis dyno and destroyed several sets of tires. It was a humbling process.
In all studies, the stock stamped steel AAM (American Axle Manufacturing) was used as a baseline. Competitive covers tested included Mag-Hytec, AFE, ATS, BD, PPE and others, with Mag-Hytec and AFE representing the ‘flat-back” design category.
After affixing anemometers fore and aft of the rear differential, a dead zone was discovered. Like the wing of plane, the rear differential splits the air. At a road speed of 70 mph, air speed was measured at 32 MPH in front of the differential and 11 MPH 20” behind the differential. This indicated an area of dead air.
This low velocity dead zone extends as far out as 36” from the back face of the cover. No matter how deep the cooling fins are, they’re unable to adequately reject heat due to inadequate airflow over the surface of the fins.
This discovery resulted in the Ram-Air scoop concept. As the truck moves through the air, cool static air is forced into the Ram-Air scoops and directed 90° up and through the long, thin heat radiation fins.
The Banks differential cover is fundamentally different from its competition because it utilizes Ram-air scoops that direct air through channeled fins, cooling the differential and internal oil temperatures.
The competition has no way of directing airflow, their covers leave a deadzone so temperatures rise faster and fall slower, meaning your oil works harder and components wear faster, costing you fuel economy.
The Banks Ram-Air cover features 169% more exterior heat radiation surface area and 21% more internal heat absorption surface area than Mag-Hytec. This is impressive considering the Banks cover retains the stock 4-quart fluid capacity.
Road tests were performed on a stretch of California’s infamous Grapevine (Interstate 5) on the same truck, with the same driver and the same load, at the same time of day and at same temperature. Starting with a nominal 78° ambient temperature, the operator pulled an 11,650 lb weight trailer. Gross combined weight was 19,750 lbs. The rear differential was heated by maintaining a constant speed of 55 mph up a 6% grade for 5 miles, ascending over 1,600’.
At the top of the 550 second hill climb, running the 3.9 quart stock differential cover, the lubricant temp was 205°. Filled with 7.5 quarts, the Mag-Hytec recorded 199° while the Banks filled with 4 quarts recorded 192.5°. Even with less lubricant, the Ram-Air cover controlled heat 2X better than the flat-back during the high horsepower hill climb!
From the crest to the end of the test, running 55 mph for 700 second at relatively constant elevation, the stock cover cooled from 205° to 195°. The Mag-Hytec cooled to 192.5° and 178.5° for Banks, a 5X improvement over the Mag-Hytec and by extension all other flat-back copies.
This test was used to determine high load, steady state thermal management. Gale had originally requested a 90 minute, 250 hp test. Gale soon regretted that request. At 90 minutes the lubrication measured 316° and was still climbing. The intense test even resulted in the dyno catching on fire. After repairs were made, the test was revised to 60 minutes at 200 hp.
Testing was started after a 100° nominal temperature was achieved. The truck was brought to 60 mph and loaded to 200 hp, typical of pulling a heavily loaded trailer up a 6% grade. Lubrication was changed between every test.
The equivalent of 60 MPH road speed air was directed under the truck’s belly using the Banks Wind Machine, aided by additional shop fans. Air damns were constructed to contain the airflow under the truck toward the rear differential.
At the end of the 60 minutes test, the lubrication temp was 289°, AFE was 261° or 28° cooler than stock. Banks was 228° or 61° less than stock. Banks outcooled AFE by 118% and by extension, all flatback covers.
Our patented Ram-Air scoops are designed to increase airflow over the rear differential without sacrificing ground clearance. In fact, our differential cover retains the same lowpoint as factory and competitors.
We searched for information on every popular brand of gear oil. The only company with in-depth knowledge and the willingness to share it was AMSOIL. In objective testing they outscored their competition in every way. They are every bit as thorough in their development as we are. The more info we discovered, the more we liked how AMSOIL designs and test their products. If you want to see for yourself, here is a link to their 75w90 test results.
We decided to stick with the manufacturer's suggested 75w90 viscosity and we chose AMSOIL Severe Gear Synthetic Extreme Pressure Gear Lube. A gear lube is only as good as it's weakest link. With more horsepower, more towing capacity, higher hauling limits, and changes in vehicle, more stress is being placed on differential gears and bearings. Our suggestion is to install AMSOIL right out of the box. That's why we teamed up with them. To find out more about AMSOIL, visit their website at AMSOIL.com
Fuel Economy was tested on the Mustang dyno using the OBD-II fuel flow rate and vehicle speed data, as well as the Banks emissions analyzer to measure fuel economy calculated from tailpipe emissions. The dyno was calibrated to simulate a 7,500 lb vehicle with an engine output of 30 HP required to maintain a 50 mph steady state speed. The truck was warmed to operating temperature then held at a constant 50 mph for a fixed length of time to procure an accurate average fuel consumption. The test was repeated for all covers as per their respective manufacturer’s fill level specifications.
At $3.50 per gallon of diesel, Flatback owners will spend approximately $447 in lost fuel economy over stock, enough money to buy another diff cover.
Use these diagrams below to help make sure the Banks Differential Cover will fit your vehicle. On most trucks, there is plenty of clearance. But just in case you may have something that can cause fitment issues, these guides will allow you to test before purchasing.