Crankshafts do not just break from big power. They break when firing pulses keep twisting the crank and that vibration is allowed to reverberate through the throws, mains, and nose of the crank. On a high-RPM, high-cylinder-pressure Duramax build, the stock elastomer damper becomes a weak link because it is tuned to a narrow frequency range and its rubber changes as heat builds. The fix here is a viscous damper. Instead of relying on rubber, it uses an internal inertia ring coupled through silicone fluid. As the crank accelerates from each firing event, the fluid shears and converts that twist energy into heat. That gives you damping over a much broader range, which matters when RPM, boost, and cylinder pressure are no longer stock. We also addressed the hardware around it. The hub is double-keyed, uses a diamond-dust friction washer, and drives the damper through pins so the bolts are not asked to locate the assembly or carry drive torque. On the L5P program, moving the crank trigger to the front also frees the rear of the crank for proper counterweighting on a racing-style crankshaft. The point is simple: control torsional vibration, reduce bending load at the nose, and keep the crank and main bearings alive when the engine is pushed well past stock output.
The video opens with Gale unboxing a new Banks vibration damper assembly for a Duramax build. The unit comes from Vibra-Tite TVD in the Buffalo, New York area, a family-run company operated by the Herschel brothers and their extended family. Vibra-Tite TVD manufactures Fluidampr products and also builds Banks viscous vibration dampers. Gale explains that Banks defines the damper requirements, then works with the manufacturer to determine the science behind the final design, including the required mass and tuning characteristics.
The first component removed from the box is the hub, which mounts directly to the crankshaft. It includes a diamond-dust friction washer that sits between the hub and the crank gear. When the retaining bolt is tightened, that washer creates the friction couple that transmits virtually all of the torque through the mating surfaces. The assembly is double-keyed, and the original equipment keyway is marked so the installer cannot accidentally place the hub 180 degrees out of position. That matters because the assembly includes a counterweight, and its orientation must be correct for proper balance.
Gale points out that the Duramax L5P version uses the standard 6-rib belt plane, but the pulley diameter has been reduced from stock. The reason is that this engine will be operated at much higher speed, with the intended limit moving from about 2,800 rpm to 3,800 rpm. Reducing the pulley diameter by 10 percent slows the accessory drive by roughly the same amount. That helps prevent overspeeding the accessories at high engine speed while still keeping the alternator fast enough at idle to maintain adequate output.
The hub also incorporates Banks' drive-pin arrangement, a feature Gale says the company pioneered years ago. In this design, the bolts do not locate the damper and do not carry the drive torque from the hub into the damper body. Instead, pins on the hub engage matching bores in the damper. That prevents bolt shear and eliminates slip between the two parts. The front face still retains multiple bolt patterns: six bolts secure the damper to the hub, while six additional threaded holes can be used to mount other driven components such as a blower pulley, a pump drive, or an auxiliary cooling-system pump. The outer diameter is configured as an 8.5-inch, 12-rib flat-belt drive intended for future supercharger use, including a planned Whipple blower application.
A second package contains prototype CNC-machined parts from Photolabs for the crank trigger conversion. On the L5P, the factory crank trigger is located at the rear of the crankshaft. Gale is relocating that trigger to the front so the rear of the crank can use a standard racing counterweight arrangement without compromise.
The conversion includes a bracket that mounts the original crank sensor at the front timing cover, along with a plug for the original sensor opening in the rear of the block so oil cannot escape. The trigger wheel is integrated into the front hub assembly, and once installed it runs with the proper air gap to the relocated sensor. This creates a front-mounted crank trigger system while freeing the rear of the crankshaft for a more competition-oriented counterweight layout.
Using a stock L5P crankshaft as an example, Gale shows the factory timing or trigger wheel mounted at the rear throw. In his view, that arrangement compromises rear counterweight mass, and he wants to avoid that compromise. His broader goal is to move as much mass inward as possible rather than carrying counterweight mass farther outboard where it increases bending loads.
The main concern is the bending moment imposed on the nose of the crankshaft by an external counterweight. Gale says that with stock counterweight mass, the load becomes severe as rpm rises. He cites a calculated bending moment of 7,200 pounds at 6,000 rpm. In that condition, the crankshaft nose is bent in the direction of the counterweight, using the first main bearing as a fulcrum and transmitting bending load through the front rod journal into the second main. Banks verified this the hard way by destroying an engine. At about 6,300 rpm with full counterweight mass, the front main was damaged and the second main was completely destroyed. The crank itself survived because it was a Bryant billet crankshaft made by Sonny Bryant, but the bearing structure did not.
Gale then shows what a broken stock crankshaft looks like at the front throw. He says this type of failure is commonly associated with the external counterweight, especially when the governor has been defeated, engine speed has been increased, and the stock counterweighted damper is still in use. He adds that firing-order effects can also contribute, and notes that some builders have broken internally balanced crankshafts as well, so the problem is not limited to one balance strategy.
Banks is developing two versions of this damper system: one with a counterweight and one without. The counterweighted version shown here is intended to work with a stock crank assembly without requiring the rotating and reciprocating assembly to be rebalanced. Gale says Vibra-Tite verified that after machining, the hub was checked on a balancing machine and confirmed to match the stock out-of-balance condition. That means it can be installed on an otherwise stock-balanced engine while preserving the original balance target.
To explain the larger engine program, Gale switches from the stock crank to the Banks big pin Duramax crankshaft. Banks developed this crank several years earlier for its own use. It is a stroker design with the rod journals moved outward to increase stroke. Combined with a 0.5 mm overbore, the displacement grows from 6.6 liters to exactly 7.0 liters.
Increasing the rod journal diameter was critical because moving the pins outward reduces overlap between the rod journal and the main journal. Less overlap weakens the crankshaft and makes the throws easier to break. By enlarging the pins, Banks preserved, and even slightly increased, the pin-to-main overlap. That required a unique rod bearing diameter that Gale says had never been used anywhere before. Banks then designed a matching connecting rod. The big end became so large that a conventional straight-split rod could not pass through the cylinder bore during assembly, so the rod uses a canted split line. Gale notes that this approach has long been used in diesel engines, but not in a Duramax. With the front trigger conversion, this crank can retain full rear counterweight capability, including the largest rear counterweight mass, without the stock rear trigger wheel getting in the way.
Gale next explains the torsional problem the damper is meant to control. When a cylinder fires, combustion pushes on the crank pin through the connecting rod and twists the crankshaft like a torsion bar. After the firing event ends, the crankshaft springs back. That twist is not isolated to one throw; it travels through the crankshaft and accelerates the flywheel, torque converter clutch mass, transmission, driveshaft, differential, axles, and ultimately the tires. Since the tires are effectively trying to rotate the world, the rear of the crankshaft is heavily anchored while the front throws are introducing repeated torque pulses.
If those pulses are not controlled, the crankshaft continues to oscillate and can resonate. Gale describes a demonstration using two torsion-bar setups preloaded equally and released at the same time. One uses only an inertial element, while the other uses a viscous damper. The undamped setup continues oscillating, while the viscous-damped setup quickly slows and comes to rest. That is the basic reason for placing a damper on the front of the crankshaft: to prevent torsional energy from reverberating through the crank and exciting other throws.
He adds that the problem is not only rotational. As multiple power pulses move through the crankshaft, the crank also tries to distort along its centerline. The main bearings and main caps are what hold it in line. Looking at the bottom of a Duramax block with its five main caps, Gale says one of the first signs of inadequate damping is damage to the mains. If the crankshaft is not properly damped, it will begin to beat out the main bearings and main-bearing structure.
The stock 2017-2019 L5P damper is an elastomeric design with a center hub, a rubber layer, and an outer inertia ring. As the crank rotates, the hub moves first, the rubber distorts, and then the outer ring follows. Gale says this type of damper can be tuned to a specific vibration frequency, but only over a narrow range, roughly 50 Hz. On a V8, he calculates that at 6,000 rpm there are four firing events per revolution, or 24,000 torque inputs per minute, which equals 400 hits per second. If the critical torsional problem occurs at 250 hits per second, corresponding to about 3,750 rpm, then a 50 Hz tuning window only covers about 750 rpm. Outside that range, the elastomeric damper is much less effective, and it may not address secondary peaks at all.
The viscous damper works differently. Inside the housing is an inertia ring suspended in a silicone fluid. The concept dates back to 1910, but Gale says it became practical in the mid-1940s after Dow Corning developed silicone fluid. The fluid used in this type of damper is about 45,000 times thicker than 30-weight oil and remains stable across a wide temperature range. Unlike rubber, which changes durometer with temperature and degrades over time, the silicone maintains a nearly constant shear characteristic from very cold conditions to several hundred degrees. When the crankshaft accelerates the damper housing, the inertia ring lags behind because it is coupled only through the fluid. The fluid shears, converting torsional energy into heat.
Gale emphasizes that a viscous damper is highly tunable. Engineers can vary the inertia-ring mass, diameter, width, and material, using cast iron, steel, or bronze depending on the required density. They can also change the viscosity of the fluid and the internal clearances between the ring and housing. Banks measures crank twist on a running engine using front and rear trigger wheels with a laser-optic system, identifies the worst-case amplitude, and tunes the damper for that condition. Unlike an elastomeric damper, however, the viscous design remains broadband rather than narrowly tuned.
The final argument is practical. The OEM damper is tuned for a stock crankshaft and stock cylinder pressure. Once the engine is modified, cylinder pressure rises, crank twist increases, and the stock rubber damper is no longer operating in the environment it was designed for. Gale says this is already visible on the "Killing a Duramax" engine, where at 3,300 rpm and 852 horsepower the stock damper's rubber is beginning to fail. Even before visible damage appears, the added energy heats the rubber, changes its durometer, and shifts the tuned frequency away from the original critical point.
That means a stock elastomeric damper is already a poor choice for a mildly hot-rodded engine, and it becomes completely unsuitable once the crankshaft and internal parts are changed for serious racing use. A viscous damper, by contrast, can tolerate changes in tune, cylinder pressure, intercooling, and overall engine output while continuing to provide a safer vibration environment. Gale concludes that although the viscous design is more expensive, it is the appropriate choice when substantial money has been invested in the engine and supporting hardware. The next step for this particular damper is installation on the "Killing a Duramax" engine and dyno testing.