Aluminum Differential Cover Thermal Results

[Blacklane]

I recently installed a finned aluminum differential cover from PML Covers on my 2012 Chevrolet Avalanche 1500 that I intend to use for towing a travel trailer. In my previous truck, I had to replace the differential bearings, which is not a small task, so I wanted an easy way to drain and fill the fluid regularly in the hope of avoiding the same problem in my newer truck. So I wanted a good differential cover with drain and fill plugs.

I powder-coated the cover in gloss black to match everything else under my truck. Installation was simple. I replaced the differential fluid with AMSOIL Severe Gear 75W90. I used a paper gasket and used medium loc-tite on the screws. (I once had some diff screws loosen causing a loss of fluid).

I have a thermal camera and I had a chance to take thermal images of the differential before and after installing the PML cover. I took both images after towing a trailer for about an hour on a highway, followed by about fifteen minutes of slower, steady driving. I could not perfectly duplicate the ambient temperature, so one image is at 70F degrees ambient and the other is at 80F degrees. In the thermal images, you can determine the ambient temperature by looking at the frame temperature in the background, which is pink/purple/blue.

I assumed that the stock differential and axle had plenty of heat-dissipating area, since the oil can flow all the way down both axle tubes. A few square inches of aluminum fins would not add much. The thermal images revealed a different story. The stock differential temperature was mostly 170-200 degrees F while the PML differential was mostly 140-150 degrees F. The axle tubes are green colored, indicating that little heat is transferred down the axle tubes.



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Click For Full-Size Image.


Click For Full-Size Image.


Full disclosure: I also sent this info to PML Covers who posted it on their website and sent me a tee shirt, so I guess you could say I have a bias. However, I think these results would be applicable to any similar differential cover.

[GordonThree]

Am I missing something? 10 degree lower ambient, 10 degree lower device under test?

[Blacklane]

Yes. My previous truck was also a Chevrolet Avalanche 1500, but a 2004 model. I used it to tow a similar travel trailer: roughly 4000 lbs dry and GVWR of nearly 6000 lbs.

I only tow a few times per year, but I had to replace the 4 differential bearings and 2 rear wheel bearings at around 160,000 miles. All of them had severe pitting.

[garyemunson]

Are you sure you were operating within the weight limits of the previous truck? Was it also a Chevy? Chevy rear ends are pretty bulletproof if kept within design capacity loads (and should not run hot).

[Blacklane]

Sorry. I tried to control the variables the best I could, but I did not perform a multi-variable controlled experiment isolating the cover and the fluid.

The first measurement was made with the stock cover and stock fluid, the second measurement was made with a PML cover and AMSOIL. I tried to take both measurements after similar towing events in similar ambient temperatures, but there are differences there as well.

You will have to draw your own conclusions about the effects of each.

[gbopp]

Wow, some people will do anything for a free T-shirt. :B

Thanks for posting, this is very interesting information.

Trackrig has a very good point. Was the old cover tested with Amsoil?

[Trackrig]

Was the previous oil a synthetic oil also? If not, the new synthetic may have assisted with the cooler temperatures.

Bill