A built Allison 1000 has to do more than survive a parts list. The hard parts matter—billet shafts, upgraded hubs, heavier components—but the real make-or-break point is how the clutch packs are configured and how the hydraulics apply them. We’re after the right clutch count, the right steel and friction thickness, the right material for static versus dynamic clutch duty, and the right clearance so the transmission can bring a clutch on cleanly without flare or excess heat. That is why the valve body matters as much as the rotating assembly. Line pressure alone does not tell the whole story. What matters is clutch-pack pressure, apply rate, and how the hydraulic system ramps the clutch on through each gear. Get that wrong and a big-power Allison will abuse the clutches even with upgraded internals. Get it right and the transmission can shift cleanly and live under serious torque. This build also shows why pre-lubrication matters. Instead of going straight into a vehicle dry after assembly, the unit is filled on the dyno, the clutch packs are saturated, and the transmission is run in neutral before testing. That gives the clutches proper lubrication before the real load starts.
This episode centers on assembling an upgraded Allison transmission for the Banks Lockjaw project. Gale calls Clint to discuss the build and asks for one of his performance Allison units to support the truck. For this application, the target is a roughly 1,000-horsepower-capable transmission rather than a stock rebuild, so the plan includes billet shafts, upgraded clutch packs, heavy-duty internal components, and a Co-Pilot-controlled hydraulic strategy. Gale also asks for the transmission to keep a subdued, rat-rod look, so the case is prepared in black instead of the builder's usual purple finish.
Clint explains that the Allison 1000 already starts with unusually large hard parts for a light-duty transmission. The planets are large, the shafts are substantial, and the clutch packs are already massive by pickup-truck standards. The performance build therefore does not depend on reinventing the transmission's basic architecture. Instead, the work focuses on strengthening the known weak points, increasing clutch capacity intelligently, and refining the hydraulic and electronic control so the transmission can survive high torque without sacrificing shift quality.
The assembly process begins with the core principle behind the build: maximizing clutch holding power without creating new problems. Clint explains that simply adding more frictions is not always an improvement. If additional frictions force the steels to become too thin, the clutch pack can actually lose durability or performance. Over time, the builder has learned the ideal combination of clutch count, steel thickness, steel material, friction composition, and clutch clearance.
That balance depends on whether a clutch is used in a more static or dynamic role. A more static clutch is applied and then remains engaged, so the priority is maximum holding power through a high friction coefficient, or mu value, between the friction material and the steel. A more dynamic clutch sees more engagement and release activity and therefore needs a friction material better able to tolerate heat and repeated abuse. In this build, the clutch packs are modified by changing pistons and related components so the maximum practical number of clutches can be installed while preserving the correct steel-to-friction thickness combination.
Clint uses the C1 clutch pack as an example. Although the individual clutches may appear small at first glance, the pack contains many of them, creating a large total surface area. These are single-sided frictions, and the clutch is engaged in nearly all forward ranges. It may briefly release and reapply during the 4-5 shift, but for most of its life it stays applied through first, second, third, and fourth gear. Because it does not repeatedly absorb the same kind of dynamic abuse as other packs, it can be optimized for maximum holding force.
As the rotating clutch drum is assembled, Clint explains how torque moves through the transmission. The input shaft is connected to the torque converter and drives the clutch drum. In this build, the input shaft is made from billet 300M steel, making it much stronger than the factory shaft. Inside the drum, the clutch pack alternates between inner and outer splined elements. The inner spline holds one member, while the outer friction engages the hub, and that hub is connected to the intermediate shaft. This is how engine torque is transferred through the clutch assembly and into the rest of the transmission.
Assembly accuracy matters because the Allison is fully non-synchronous. The computer controls clutch application and release rates, so small mechanical details directly affect how well the transmission responds to calibration. Snap rings, for example, are directional. Installing one backward may not always ruin the build, but it can create service problems and complicate disassembly. Clint also relies on specialty tools to verify clutch clearances because each clutch pack must be set to a specific target.
Those clearances are critical to shift quality. If a clutch pack is too loose, the clutch can flare during application under high power, slipping while trying to overcome engine torque. That creates excess heat and abuse, reducing longevity. When the friction material, hydraulic modifications, clutch clearance, and TCM programming are all matched correctly, the result is a transmission that shifts cleanly at both light and high power levels.
The build continues with the C2 clutch pack and related hard parts. Clint compares a factory hub with the billet replacement, noting that the billet version is hardened steel while the factory part can twist at the planet area when power levels rise. At the intended output for this truck, stock components simply begin to break, so the upgraded hub, billet input shaft, billet intermediate shaft, and other heavy-duty parts are necessary insurance.
Throughout assembly, Torrington bearings are used to keep endplay tight. Clint points out that Torrington bearings are a major advantage over thrust washers because they allow much more precise control of internal movement. Assembly lube is used to keep components from floating around during installation and to hold clutch elements in place while the stack is built.
He also emphasizes the importance of stack height and endplay. Once hubs, drums, and clutch packs are modified, there is only so much room available in the transmission. If the clutch packs are stacked incorrectly or the endplay is not tightened properly, the rotating assembly can develop lateral movement. That allows parts to flop around internally, which is unacceptable in a high-power build. The completed rotating clutch drum assembly houses the C1 and C2 clutches and is directly tied to the input shaft, making it one of the most heavily loaded parts in the transmission.
Clint then explains why the input side of the Allison sees such extreme loads. The torque converter's stator multiplies torque as fluid leaves the impeller, strikes the turbine, and is redirected. With the billet stator in place, the multiplication effect can produce as much as roughly twice the engine's torque at the input shaft. If the engine is making 1,000 lb-ft, the input shaft can see up to 2,000 lb-ft. That is why input shafts are among the first parts to fail at high power and why this build uses billet components.
From there, assembly shifts to the case. Clint prefers to build the Allison from the back side in this sequence because it simplifies shimming and endplay setup. He installs the hydraulic piston into the case and explains that the piston's effective area, multiplied by hydraulic pressure in PSI, determines the lifting force applied to the clutch pack. That force squeezes the clutches together and locks the relevant member to the case.
For viewers familiar with older transmissions that used bands, he notes that modern units like this Allison do not use bands in the same way. Instead, when a clutch pack ties a rotating member to the case, it performs the same functional role as a brake band. In other words, these brake clutches are what hold portions of the planetary gearset stationary during operation.
The rear of the transmission is assembled with the low clutches, or C5s, followed by the C4s and then the C3 section later in the process. Clint pays close attention to the orientation of steels and their lubrication slots. Those slots serve two purposes. First, they provide lubrication. Second, they help reduce friction coefficient when the clutch is disengaged so the clutch pack does not drag excessively while the vehicle is moving.
Reducing drag is important for efficiency. A disengaged clutch that continues to drag wastes energy and hurts economy. Clint notes that some clutch designs in other applications may omit lube slots or use different scallop patterns, but modern clutch design can provide both strong holding power and low drag when released. Different manufacturers approach this differently, yet the goal remains the same: durability, holding force, and clean release.
The planetary assembly is then installed. Once again, Clint remarks on the sheer size of the Allison's planets, describing them as monsters. The gearset, billet output, billet intermediate, and the C4 and C5 clutch assemblies are secured, torqued, and checked before the transmission is flipped over for the next stage. By this point, the back half of the transmission is effectively built and ready for the remaining clutch pack and pump installation.
Next comes the C3 clutch pack, which Clint considers the most important clutch pack in the Allison. He spends extra time here to fit as many clutches as possible while maintaining the correct clearance and stack-up. The C3s are especially problematic because they must apply in third gear and fifth gear, where they tend to absorb significant abuse. For that reason, this clutch pack receives particular attention during the build.
Once the C3s are installed and retained with a heavy snap ring, the pump is prepared. Clint describes the pump as the heart of the Allison and notes that the factory transmission already starts with a robust pump design. Even so, the final setup still depends on precise overall endplay. After the entire clutch stack and geartrain are assembled, the target is to bring total endplay down to nearly zero, typically about 0.010 to 0.012 inch. That gives the assembly just enough room to float as the transmission heats up and the case expands, while still keeping everything tightly controlled.
With the internal assembly complete, attention turns to the valve body and external finishing details. Clint realizes that the intended vehicle installation will not work well with the usual deep pan, so he plans to replace it with one of his shallow pans. That is a packaging decision rather than a performance downgrade, since most of his builds normally leave with a deep pan.
Clint describes the valve body as the transmission's brain and stresses that hydraulics are half the build. A transmission can have excellent hard parts and clutch packs, but if the valve body is not built correctly, the unit has little chance of surviving. To verify the hydraulic system, he runs the Allison six-speed valve body on a test machine that simulates the vehicle and transmission. Each gauge on the fixture corresponds to an actual clutch pack, allowing him to monitor main line pressure and individual clutch-pack pressure through first, second, third, fourth, fifth, and sixth gear, as well as lockup and downshift events.
The modified transmission is designed to make about 275 to 280 PSI of line pressure, and with Clint's pump and valve body work it will be just short of 300 PSI. However, one of the key Allison limitations is that clutch packs do not automatically receive full line pressure. A gauge on the transmission can show line pressure, but it does not reveal actual clutch-pack pressure. On the test fixture, Clint can see that while line pressure is around 280 PSI, clutch-pack pressure may only be about 165 PSI if the Co-Pilot-controlled solenoid is not engaged.
That is where the Co-Pilot system becomes essential. The computer program modulates the solenoid, the solenoid applies low pressure to a spool valve, the spool valve routes line pressure through the valve body to the trim valve, and the trim valve then feeds the clutch pack. The test transducer emulates the clutch pack so Clint can observe the actual hydraulic behavior. His goal is to make clutch-pack pressure match line pressure at the right time, while still ramping the clutch on smoothly enough to avoid an overly aggressive shift. He cycles through the full operating range, looking for anomalies and confirming that the hydraulic map behaves exactly as intended.
By the end of the episode, the upgraded Banks Allison 1000 six-speed is essentially complete as a high-power unit built around billet shafts, reinforced hubs, carefully selected clutch materials, increased clutch counts, controlled endplay, and a thoroughly validated hydraulic system. The build preserves the Allison's inherent strengths while addressing the areas that fail first when torque rises sharply, especially at the input side where converter multiplication can double the load seen by the shaft.
Clint closes by expressing enthusiasm for the project and appreciation for the collaboration with Banks. He emphasizes that the transmission build is not just about stronger parts, but about integrating mechanical upgrades, hydraulic control, and electronic strategy into one coherent package. The next episode shifts away from the transmission and back to the Lockjaw chassis, where Gale begins laying the chassis on the ground and discussing the sheet-metal work needed to move the truck forward.