Challenger SRT 392
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Yeah was thinking about the load or maybe lack of it being a factor. More load I could see hurting things along with excessive heat. Less load with over rev but we have rev limiters so would over rev from too light of a load be sort of protected against or no?The problem seen here can be caused a number of different ways. First, dynos generally have variable load settings dependent upon the vehicle's weight and HP rating. If running a pull at too high or too low of a load. If the load is calculated too high, it can stress the transmission and drivetrain similarly to the effect of pulling a load that's too heavy for the vehicle.This is my guess as to the root cause. The reason why they run them on a load is to account for simulated road friction/aero effects, and a dyno with no load can force over rev issues. Those rollers weigh in excess of 2,500lb, and that's a lot of rotational mass if they're not magnetically held back. Then, of course, maybe the guy's transmission was damaged or modified and it was just its time. But, more than likely, they ran the car through all 8 gears into overdrive and the overdrive gears can't handle the torque of the engine combined with the increased load on the dyno rollers. User error, 100%.
As others have mentioned, it's normal to do a pull in the single highest, non-overdrive gear when measuring torque/horsepower potential. My guess is they were trying to do a high speed run as part of some sort of dyno battle or some such.
I'm not a transmission guy, so I apologize if I say something wrong here. But, overdrive gears are cruising gears. They're not bolstered for accepting high torque applications. If you look under the car on the dyno, you see all those transmission guts. It is my guesstimate that they were trying to run the car to 240mph or some such through 7th or 8th gear and it literally blew the trans apart. Normally under road conditions, there's less force being applied to the trans in overdrive gear(s). On a dyno, the load is fairly constant once the tester sets the magnetic load. IRL, if you put the car in manual mode in 8th gear at 65 mph, you accelerate very slowly and it feels like the engine is lagging a bit. On a dyno, the rotational mass of the cylinder is actually helping you turn the transmission in overdrive, and thus imparting a lot of that artificial load force directly into the transmission where it should not be. So, while Dodge says you can get max speed of 203mph or whatever in 6th, theoretically you can get more out of continuing to run it in 7th/8th in a test environment, like say with the wheels up on a lift. But, when you add in the artificial load (which is just as strong at 40mph on the Dyno as it is at 220mph), the more fragile 7th/8th overdrive gears probably couldn't take the stress and detonated something, which blew the entire pan off the trans and lord known what else in there.Yeah was thinking about the load or maybe lack of it being a factor. More load I could see hurting things along with excessive heat. Less load with over rev but we have rev limiters so would over rev from too light of a load be sort of protected against or no?