The Allison 1000 transmission was introduced in 1999 as an electronically controlled 5-speed automatic transmission for on-highway medium and heavy duty trucks. In 2005 a 6th gear was added to create a double-overdrive with a manual gear selection option to give drivers more control when less shifting is needed or when engine braking. Allison 1000 weaknesses can include uneven wear and early failure of the C1, C2, and C3 clutch plates. The issues can be caused by lack of even pressure and clutch lubrication. Raybestos Powertrain addresses these common failures with several aftermarket solutions that include the use of GPZ friction material to increase clutch life and durability in high-stress driven vehicles. Additional friction and steel clutch plates are also available in our GPZ Torqkits to increase performance.