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 manufactures, 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.
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.
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 increases 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.
Fitment Notes: Fits 2001-2019 Chevy/GMC/Dodge/Ram vehicles with AAM 11.5" and 11.8" 14-bolt rear differential cover.
Check clearance, fitment and confirm your truck has the correct differential before purchasing.
BANKS RAM-AIR REAR DIFFERENTIAL COVER
Features and Benefits
- Banks cools 4X better than flat-back covers in on-road towing tests over the same road, same weather, operator and vehicle
- Banks cools 118% better than flat-back covers in controlled 200hp 60mph sustained dyno tests
- New patented design features Ram-Air scoops
- Forces air up and into massive heat radiation fins providing the fastest cooling on the market
- Provides cold high velocity air, overcoming “dead air zone” behind differential
- Engineered to break-away if snagged on an obstacle
- Internal heat absorption fins transfer heat through the cover to the external fins
- Dry-mount high-pressure silicone O-ring seal. No messy RTV clean up when servicing differential
- Clears spare tire heat shield, Panhard bars and other suspension components
- Lowest point is the rear differential housing, not the Banks Ram-Air cover
- Limited Lifetime Warranty
- Cover mates perfectly with differential housing for unobstructed fluid flow
- Ring gear controls the fluid flow path to the pinion and bearing sets
- Axle tube lubricant guides direct fluid to axle bearings without over-filling
- Low fluid aeration means longer fluid life
- No need to remove cover to change fluid
- Magnetic 3/8” drain plug with 3.8” square drive, no hex wrench required
- Magnetic 3/4” fill port plug with 3/8” square drive, no hex wrench required
- 20° angled fill port for easy access
- 1/2” Stainless steel sight glass with contrast screen (visual aid) and Viton seal
- Banks recommends Amsoil 75W-90 Severe Gear Synthetic Gear Lube Easy Pack
- Finish: Satin black textured powder coat or as-cast aluminum
- Material: A380 aluminum diecast with CNC machined surfaces
- Weight: 11.7 lbs
- Dimensions: 14.2” X 13.3” X 3.8”
- Internal volume: 4 quarts matching factory fill level
- External heat radiation fin count: 24
- Internal heat absorption fin count: 26
- External heat radiation fin surface area: 533.782 inches
- Internal heat absorption fin surface area: 119.882 inches
- External heat radiation total surface area: 808.81 in2
- Internal heat absorption total surface area: 215.78 in2
- Fasteners: Chrome-plated 12-poing flanged M8-1.25x32mm bolts
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.
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.
Heat Absorption and Radiation Surface Area Comparison
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 Test: Heat Rejection — Grapevine Trailer Test
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 with a 2018 Chevy Silverado 2500HD 6.6L diesel. 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 4X improvement over the Mag-Hytec and by extension all other flat-back copies.
Chassis Dyno Testing: Heat Rejection — Sustained Power Test
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. Using a 2007 Dodge Ram 6.7L 3500 dually, the truck was brought 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.
Anemometer: Air Velocity
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.
Fuel Economy Testing Simulated City Driving
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, Banks owners will save $251 in fuel for every 100,000 miles driven as compared to stock. Flatback owners will spend approximately $447 in lost fuel economy over stock, enough money to buy another diff cover. Those upgrading from a flat-back design to a Banks cover can will see a $697 savings in fuel economy over their next 100,000 miles.