Differential heat is a sustained-load problem, not a quick-hit problem. That is why we set up rear differential cover testing around two hours at 250 horsepower and 70 mph to the ground. The weak link turned out to be the dyno, not the test. The absorbers hit 653°F in three and a half minutes, which we later confirmed was their operating limit, and the unit eventually caught fire near the end of the differential cover work. We had already added blower airflow to protect the tires during long runs, and now that airflow is being redirected to the absorbers so the dyno can survive the kind of continuous thermal load this testing demands. The point is simple: if you want to understand differential cooling, you have to test for real sustained heat, not just make a short pull and call it done.
Gale Banks reports that Banks Power severely overheated its chassis dyno during differential cover testing. The test plan was straightforward but demanding: hold 250 horsepower to the ground at 70 miles per hour for two hours. According to Banks, the team completed that load request, but the dyno did not tolerate it. Near the end of the testing, the unit burst into flames.
The failed unit was a Mustang dyno marketed as a 750-horsepower dyno. Banks emphasizes that the team was not attempting anything close to that peak number; they were asking it to sustain only 250 horsepower. The problem, as he describes it, was not peak capability but continuous-duty endurance. In practice, the dyno could not survive that sustained load for the intended duration.
After the incident, the team determined that the dyno reached 653 degrees Fahrenheit after only three and a half minutes at 250 horsepower. Banks says they later learned that 653 degrees Fahrenheit is effectively the operating limit. That finding made the two-hour target especially alarming, because if the system was already at its limit within minutes, the temperature later in the run would have been far beyond acceptable. Banks speculates that it could have approached 1,000 degrees Fahrenheit under those conditions.
Banks explains that, a few years earlier, the team had installed large blowers on the wall to help manage heat during dyno operation. Those blowers push air through eight 8-inch-diameter tubes and direct it onto the concrete slab beneath the vehicle. The purpose of that airflow was tire cooling. During extended dyno pulls, tire temperatures can rise enough to cause chunking, where pieces of rubber tear away and can be thrown violently toward the back wall. Banks notes that the team has experienced that kind of tire damage before, so the cooling system was originally configured to protect the tires.
In response to the dyno fire, the team is changing that airflow strategy. Instead of prioritizing the tires, they are rerouting the blower air directly to the dyno absorbers. The goal is to cool the absorber hardware itself, which appears to have been the limiting factor during the sustained 250-horsepower test. This change reflects the lesson from the failure: under long-duration load, absorber temperature management is more critical than the previous tire-focused airflow arrangement.
Banks places the incident specifically within the differential cover test program. He says the fire occurred right near the end of that testing sequence. That timing suggests the dyno had been subjected to prolonged thermal stress during the evaluation, and the accumulated heat ultimately exceeded what the absorber system could handle. His frustration is clear, but the technical takeaway is that the dyno's real continuous operating limit was exposed by this test.
Banks closes by saying he is not happy about the failure and intends to keep viewers updated as the investigation and corrective work continue. The immediate direction is to improve cooling to the absorbers and better understand the dyno's sustained-load limitations so future long-duration testing can be completed without another thermal event.