At a recent TASC™ Force meeting, one of the members expressed concern about an increase in the number of worn-out bores in TCC pistons that he was seeing. Although the problem is prevalent in many different pistons, his main focus was on the GM 298mm pistons. He went on to clarify: The worn-out bores were not being found on OE converters that were coming in for rebuild. The problem was only happening on previously rebuilt converters. The general consensus was that the problem was caused by an out-of-balance condition, and there was a great deal of speculation about why this was happening.
When the OEMs build a converter, they balance the turbine and the clutch individually to a tolerance of 1 gram-inch. The two components are then mated together, with the heavy spot of the turbine indexed directly opposite the heavy spot on the clutch. On the 298mm GM converter, the heavy spot on the turbine is located where the balance weight was added. This spot is marked with a paint dab at the factory (see Figure 1).
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Article No.: TCTIP-03-06
Author: Ed Lee
Total Pages: 2
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