The Allison LCT1000 is legendary, but in factory form, it is the primary bottleneck for the 6.6L Duramax engine. Increased tuning and heavy towing frequently lead to "Limp Mode" due to slip detection and inadequate line pressure. The ATS 2WD Allison Performance Package is a ground-up re-engineering of the LCT1000 platform, designed to handle extreme torque while providing crisp, reliable shifts.

Notable Transmission Build Specs

• Premium Foundations: All new gaskets, bushings, seals, and pistons are used during assembly.
• P1 Sun Gear Bearing Upgrade Kit: Addresses a prominent wear-induced failure point inside the factory gear train.
• ATS Allison Pump Modifications:
  • Upgraded high-volume Line-to-Lube Pressure Regulator Valve and shim kit (safely elevates line pressure and enhances lubrication throughout the hydraulic circuit) - 2001-2002 Models Only.
  • ATS Allison Cut Back Valve Upgrade - 2001-2002 Models Only.
• ATS Valve Body Modifications:
  • 2001-2005 (5-Speed): ATS F-Trim Solenoid and block upgrade, performance A and B trim valves, performance shift kit, and a modified internal wiring harness explicitly wired for Co-Pilot functionality.
  • 2006-2010 (6-Speed): Full ATS Solenoid Block upgrade featuring Performance A and B trim pressure control solenoids and a Performance Torque Converter Clutch (TCC) solenoid.
  • 2011-2019 (6-Speed): Performance A and B trim pressure control solenoids, Performance TCC solenoid, and the proprietary ATS G-Block Solenoid Upgrade to enable seamless high-line pressure control functionality.
• Heavy-Duty Engineered Clutch Packs:
  • Performance C1 Pack: Modified C1 pressure plate accompanied by (8) internal and (8) external C1 performance friction clutches.
  • Performance C2 Pack: ATS laser-cut C2 spacer, (7) C2 performance friction clutches, and (8) heavy-duty C2 steels (.086” thick).
  • Performance C3 and C4 Packs: Modified C3 and C4 pressure plates featuring (12) C3/C4 performance friction clutches, (4) C3/C4 steels (.0747” thick), and (7) C3/C4 selective steels (.105” thick).
  • Performance C5 Pack: Includes (6) C5 performance friction clutches paired with (6) thick C5 steels (.1046” thick).
• Filtration: Complete kit includes both brand-new internal filters and external spin-on filters.
• Case & Core Preparation: Transmission cases and critical hard parts are thoroughly disassembled, inspected, and solvent-cleaned. Valve body and pump castings are checked and machined to ensure perfect flatness.
• Advanced Quality Validation: Comprehensive vacuum and air checks are executed throughout the build process. Valve bodies are hydro-tested on our in-house SuperFlow valve body machine, and every completed transmission and torque converter is dyno-tested together as a matched pair.

The Deep Dive: Inside the ATS Engineering Advantage

High-Volume Pump Design & Stable Pressure Regulation

To safely manage the massive output of a tuned Duramax, an upgraded transmission requires absolute hydraulic stability. Every ATS Allison pump is modified with a high-volume, completely redesigned Pressure Regulator (PR) Valve assembly. This specialized configuration stabilizes line pressure around a powerful 275–300 PSI. Please note that our dedicated pump line-to-lube modification and the cutback valve upgrade inside the PR valve are implemented on 2001–2002 models only. For these specific early model years, this exclusive modification allows full line pressure to consistently reach the clutch packs rather than venting away, keeping vital components fully lubricated and cool under load.

The C3 & C4 Non-Vented Steel Advantage

The C3 and C4 clutch packs are notorious failure points on stock Allison transmissions due to heat and severe holding loads. While several aftermarket replacement kits utilize generic vented steel plates, ATS deliberately utilizes a solid, non-vented steel design. Vented steels drastically reduce the effective friction holding surface area by 20%. This structural reduction places extreme structural strain on the friction clutches, encouraging heat buildup and causing the clutches to start slipping much earlier in the power band. Our non-vented steels retain 100% surface area engagement for maximum thermal dissipation and unmatched holding power.

Valve Body Engineering & True Line Pressure Architecture (2001-2010 Gen 3 & Gen 4)

A common mistake in the diesel industry is relying on basic drop-in pump kits (such as Transgo kits) to boost pressure. In reality, generic pump modifications fail to provide the necessary pressure increase to the entire transmission. On 2001–2010 Gen 3 and Gen 4 builds, the factory valve body acts as a strict bottleneck; it limits the actual volume of pressure that reaches the clutch packs, regardless of what the pump generates. To circumvent this restriction, Gen 4 systems must run the ATS Co-Pilot Transmission Controller to route full line pressure straight to the clutch packs where it is actively required to hold power. This hydraulic pathway is completely updated through our proprietary ATS separator plate, unlocking the total power-holding potential of the Allison platform while delivering fast, clean, and positive gear changes.

In-House Testing & Diagnostic Validation Protocols

We do not guess at electrical or hydraulic performance. Before final assembly, every single shift solenoid is extracted and tested individually on our specialized in-house solenoid test machine to verify proper electrical resistance and mechanical speed. Furthermore, we dyno test our valve bodies on a high-end hydro-test valve body test machine. This allows our technicians to completely balance the A and B trim solenoids under real-world pressure scenarios, eliminating cross-leaks and ensuring perfectly timed clutch-to-clutch handoffs before the valve body is bolted into the casing.

ATS Five Star Torque Converter (Standard on Stage 3+)

The patented ATS Five Star Torque Converter features an industry-leading 2.4:1 torque multiplication factor, completely overshadowing the weak factory ~1.25:1 ratio. This allows the Cummins or Duramax engine to spool the turbocharger instantly, eliminating off-the-line lag.

• Patented Viskus Clutch Drive System: Features CNC laser-cut clutch plates designed for maximum efficiency.
• Square Tab Construction: Employs a robust square flank drive design on the billet cover and piston, ensuring internal clutches remain perfectly intact under high-torque engagement.
• Proprietary Bonding Technology: Our exclusive clutch formulation guarantees a 100% chemical bond to stop friction material delamination in its tracks.
• Bulletproof Construction: Reinforced with a 4340 hardened turbine spline, a high-flow CNC-machined stator with optimized oil windows, full roller-bearing internals, and a plasma-welded impeller housing.

ATS Co-Pilot Transmission Controller (2001-2010 Only)

The Co-Pilot functions as a closed-loop electronic sub-computer that continually monitors engine and vehicle dynamics to eliminate the dreaded Allison "Fail-Safe" Limp Mode. By monitoring real-time Boost Pressure (MAP), Vehicle Speed (VSS), and Throttle Position (TPS), it dynamically spikes clamping force to allow clutch packs to receive full line pressure (up to 230 PSI) right when the truck demands it.

• On-The-Fly Customization: Dash-mounted kick-panel controller lets users adjust line pressure settings seamlessly.
• Real-Time Diagnostics: Features a built-in display with sequence lights to provide real-time feedback on transmission activities.

4340 Billet Input & Intermediate Shafts

When punishing your truck with boosted launches or extreme towing weights, factory cast shafts quickly snap under the strain. Our optional billet input and intermediate shafts are CNC-machined from premium 4340 high-strength alloy steel. This structural material delivers deep hardenability, maximum fatigue resistance, and exceptional toughness to comfortably withstand extreme shock loads without twisting or fracturing.

The ATS Diesel Difference

"True transmission performance isn't built on a standard workbench with off-the-shelf parts; it's born from precise engineering and exhaustive validation. By analyzing every hydraulic constraint inside the factory Allison, we created a system that completely redefines power transmission. When you buy an ATS package, you are getting a transmission and converter that have been dyno-tested together as a matched pair, ready to deliver flawless operation out of the box."