Allison transmissions are some of the toughest and most reliable transmissions produced worldwide. The Allison 1000 and 2000s are used by various manufacturers such as GM, International, Peterbilt, and Kenworth, to name a few. To say that the name builds confidence with its customers is an understatement. The Allison nameplate is a major determining factor in the vehicle purchase decision for many customers.
Allison has always been “on the ball” when it comes to update changes to improve their products. The 1000/2000 transmissions underwent major changes in the last few years. The A1000/A2000s are transitioning starting in 2023 to a new 9-speed unit, the MD9. While the A1000/A2000 are still available, the MD9 will surely dominate the industry in short order.
In the style of Allison, rather than “throwing the baby out with the bathwater” as many other manufacturers do when a new unit is introduced, Allison incorporated the A1000/A2000 design’s success into the new MD9. The MD9 shares about 70% of its components with the A1000/A2000. GM no longer uses the LCT 1000/LCT 2000 as they changed to the 10L1000 application starting in 2020.
Before the updated MD9 was introduced, Allison made several changes to the A1000/A2000 series units. The updates I am referring to were introduced for the 2020-2022 applications. These updates are not used with the GM units, as they were implemented after GM introduced the 10L1000. 2020-2022 updates include:
- P2 Carrier Update – The P2 Carrier was updated due to cracks caused by vibration-related vehicle issues (Figure 1). This was a common issue in many applications, such as dump trucks and garbage trucks.
- Issues such as u-joint working angle, drive shaft balance, worn u-joints, and engine and differential-related vibrations can damage the P2 carrier. To address the issue, the new P2 carrier received the following changes:
- Removal of the snout bushing oil annulus.
- Moving the bushing shoulder to eliminate stress cracks in the oil hole area.
- Burnishing the lube passages to eliminate stress.
Other changes include:
- Updated C1 Housing Snap Ring.
- Updated C5 Piston Outer Seal.
- Updated P3 Retaining Ring Design.
- The P1 and T3 thrust bearings were updated to increase thrust capacity.
- GEN 6 controls: The GEN 6 control module, C71M, C72M, and C73M were introduced to improve cyber security, incorporate a “Flex Can Data” (CAN FD) communication system for module to module, and data communications with your scan tool. The Gen 6 module includes unique features such as controller wake up anytime a CAN message is sent (Wake On CAN), which eliminates the need for ignition input to wake up the module. In addition, the Gen 6 module is compatible with analog and digital speed sensors, as were some of the earlier TCMs.
Gen 6 controls were introduced on October 15, 2021, for use in 2022 A1000, A2000, A3000 and A4000 applications. The GEN 6 TCM “IS NOT INTERCHANGABLE” with earlier design systems. The GEN 6 Module fits multiple applications. The GEN 6 system TCM utilizes an 80-pin connector and attachment, so you need to replace it with the correct generation module (Figure 2).
With the updated GEN 6 control package, the DTCs also made some changes. The GEN 6 controls utilize several new and updated DTC’s including:
- P0600 Solenoid Controller Serial Peripheral Interface Communication
- P0604 Bus Off Control Module Random Access Memory (RAM)
- P060C Internal Control Module Main Processor Performance
- P0652 Sensor Reference Voltage B Circuit Fault
- P0720 Output Shaft Speed Sensor Circuit
- P0721 Output Shaft Speed Sensor Circuit – Performance
- P0722 Output Shaft Speed Sensor Circuit – No Signal
- P0965 Pressure Control Solenoid (PCS) 2 System Performance
- P0969 Pressure Control Solenoid (PCS) 3 System Performance
- P2728 Pressure Control Solenoid (PCS) 1 System Performance
- P2762 Torque Converter Clutch (TCC) Pressure Control Solenoid (PCS)
- P27B2 Internal Control Module Transmission Control Circuit Range/Performance
- P27B4 Internal Control Module Transmission Gear Direction Performance
- P27B6 Internal Control Module Transmission Gear Speed Sensor Performance
- U0103 Lost Communication with Gear Shift Module 1
- U0304 Gear Shift Module 1 Incompatible
- U0404 Gear Shift Module 1 Invalid Data
- U1401 J1939 TSC1 Engine Message Impostor Detected
- U1402 J1939 TSC1 Compression Brake Message Impostor Detected
- U1403 J1939 TSC1 Exhaust Brake Message Impostor Detected
It might seem like a lot of changes when the units seem destined to be phased out down the road, but keep in mind the new MD9 will incorporate all of the updates and many more as Allison converts to a nine-speed application. Well, that’s about all the time we have. Until next time, remember, “The road to success is always under construction.”
