Flat Back Diff Covers Debate

Is your aftermarket cover doing harm?

Published in the March 2020 Issue February 2020 Feature Brady L. Kay

DT--Gale Banks from Harris Media Services on Vimeo.

Similar to the way a doctor swears the Hippocratic Oath not to do any harm, Gale Banks, founder of Gale Banks Engineering, feels he has a responsibility as well when it comes to aftermarket equipment. Today Banks is best known as a pioneer in automotive performance as well as a brilliant engineer and entrepreneur, but his roots go back to his racing days and that’s why his impact on the diesel segment alone is immeasurable. He has dedicated a lifetime to improving performance and that’s why he’s so adamant about the flat-back differential covers being offered in the market today.


“Flat-back diff covers do harm,” says Banks. “They do harm to the lube because they just work the living hell out of it. The fluid dynamics that the OEs have in the stock diff cover shape, you need to pay attention to that; it’s that way for a reason.”

His displeasure for flat-back diff covers – that to him is more of cosmetic billboard for a company logo than an actual performance improvement – led to the development of the new Banks Ram-Air differential cover.

“That big flat surface is a nice place to advertise so my guys in the art department got with the guys in the engineering department and drew one up in CAD,” recalls Banks. “It was a flat-back and had a Banks logo on it with a big American flag. It was real patriotic, which is right in my wheel-house.”

Banks discovered the proposed flat-back diff cover by chance as his employees were having a meeting about it and they showed him the drawings. He had been wondering about the fluid dynamics in a differential cover and immediately put a hold on the project until he could learn more.

“We’re not going to do this unless we know it won’t hurt anything,” Banks recalls announcing in that meeting. “If you’re in the racing engine business, which I’ve been for 61 years, aftermarket speed equipment should do no harm and it should make power. Do no harm is the issue here.”

After doing his own testing he quickly discovered some flaws in the flat-back diff cover design and it became apparent to him those covers do not cool as well as advertised and suffer from poor fluid dynamics.

“A stock fill is four-quarts with a curved back and I see 6-, 7.5- and even 8-quart covers and by overfilling them you’re burring the ring and pinion,” adds Banks. “In those cases some aftermarket companies appear to be solving a problem that doesn’t exist.”

During the testing process a flat-back diff cover with a Plexiglas back was used to see how the fluid was reacting inside.

“It was like a fire hose, bam, right into the back of the cover,” says Banks. “Not only was it hitting the back but it was aerating the lubricant.”

Cooling was another area where Banks knew he could improve and his new Ram-Air differential cover is able to cool up to five times better compared to flat-backs, thanks to air scoops on each side that are designed to break away if you happen to accidentally hit something. While flat-backs create dead air space behind, the scoops take advantage of the passing air in a way not seen before in our industry.

And because Banks is tired of being copied on other products he’s developed over the years, he was able to secure a patent on the design. The Banks Ram-Air differential cover that extends the lubrication life and retains fuel economy, debuted at the 2019 SEMA Show in November and is currently available in Satin Black/Machined or natural aluminum that is ready for paint.

What started out as a way to possibly display a logo turned into yet another great product development for Gale Banks Engineering which can be added to a long list of other aftermarket improvements this manufacturer is best known for.  

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