Revisiting the captive clutch

Joe Rivera proved that the ZF5HP19/24 captive clutch is rebuildable (see “Rebuilding the Unrebuildable,” Transmission Digest December 2005). Many converter shops are now attempting to build this unit, and the number of rebuilding questions continues to increase. A recent rise in lockup performance-related issues after rebuild has prompted a closer look at this unit. The same fear factor that prevented many shops from attempting to rebuild this unit in the first place is now causing some of the braver rebuilders to have second thoughts. A better understanding of the mechanics that make this converter unique should ease some of their concerns. The most unique part of this converter is the TCC piston’s very limited range of travel. The six springs that aid the forward movement of the piston are riveted to the piston on one end and the spring retainer on the other end. Since the spring retainer is friction-welded to the center tower of the converter and no provision has been made for extra travel, the piston can travel only as far as the spring can flex. This limits the total available travel of the piston to .040”. To put this into perspective, .040” is 1 millimeter, or the thickness of a dime. Looking at the piston and retainer from the bottom of the piston, the gap that you see between the piston and retainer is its available travel (see Figure 1). Place the clutch on the cover and the piston on the clutch. You may now measure the position of the spring retainer in relationship to its position before it was removed.

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Article No.: TCTIP-03-07
Author: Ed Lee
Total Pages: 2

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