Since the early days of torque converters, the contact surface between the stator cap and turbine hub has been a high wear area. The first torque converters used aluminum stator caps that ran against the cast steel turbine hubs. Material loss due to wear on the stator cap needed to be compensated for when the converter was being rebuilt. Most rebuilders viewed the wear as normal and dealt with it by using selective thrust washers and wear plates. Then came the early rear wheel drive Chryslers and early Mitsubishi front wheel drive converters. The severe wear on their stator caps forced converter rebuilders and designers to take another look at the problem and the search for a solution began. Some manufacturers dealt with the problem by installing thrust washers between the stator cap and turbine hub while others opted to change the material of the stator cap. Installing the thrust washers and changing to a phenolic material were both successful in some cases but for the most part, wear was still an issue. Installing a bearing between the stator and turbine hub seemed like the best option but limited space and the need for a tall piloting area kept the use of a bearing to a minimum. The tall piloting area was necessary because the internal forces of the converter keep the stator and turbine separated except during deceleration.
At this point most engineers were assuming that the stator cap material needed to be upgraded and that is where they focused their research. However, we all know what assuming does.
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Article No.: TCTIP-07-08
Author: Ed Lee
Total Pages: 2
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