The thing about race cars is they are purpose-built. In normal circumstances, a car built for one specific task is not worth transforming into something else. However, it has become a subculture in the car world to engage in the adventure of taking absurd machines on even more absurd adventures. Case in point: a NASCAR truck doing a week-long slog of drag races connected by a giant road trip. If you think that can’t go well … you’d be right.
We talked about this Dale Earnhardt, Sr. tribute pickup previously when it first took to the dragstrip to see what it could do, but the YouTube channel behind the truck decided to go one further and take it on Rocky Mountain Race Week 2.0 recently. The wild part is the road race chassis is not what gave them trouble.
The powertrain was the failure point, the throwout bearing specifically. From their recent re-cap post, it seems the hydraulic throw out bearing was mis-adjusted and caused one of the clutch plates of the two-plate clutch to break apart. Those who have experienced a throwout bearing failure know driving is not impossible afterward, but it is certainly not fun. Rather than give up and load the truck onto a trailer, the driver, Kevin, elected to have the truck push-started at each stop and skip-shift from first to third for the passes down the dragstrip and attempted to make up the time of the shift and gearing disadvantage by spraying the intake charge with nitrous oxide once the truck was in gear.
The truck finished the event, but the carnage held within the bell housing is a reminder of just how bad things can get when one part of a system is slightly out of adjustment. From the scars left on the clutch parts, it seems the throwout bearing was adjusted to extend too far when the pedal was depressed. This forced the fingers of the pressure plate into the spinning clutch disk, two items that should not be touching.
All those parts came out though and in went a triple-disk race clutch inside an SFI bellhousing that bolts to a face-plated transmission. Lots of jargon there so here is the rundown. Multiple clutch plates allow lower clamping force to hold more power, so upgrading from two friction plates to three will help keep the power going through the clutch without slipping while not increasing the effort required at the pedal to disengage the whole operation to shift. The SFI bellhousing is a safety item that the crew should have installed from the beginning. If any part of the very-quickly spinning clutch were to come apart, this bellhousing is rated to contain it, rather than let it slice through and into the passenger compartment. The last item is a face-plated gearbox that takes the concept of synchronizers on the gears and turns it up to 11. Just mash the shifter into gear and the modifications to the faces of the gears will make them come together. Faster shifting.
All this work seems to be pointing towards an attempt to make an eight-second quarter-mile pass. That would be pretty impressive to see, so we know we’ll be staying to tuned to see if that happens, or if another weak spot pops up instead.