The ZF6HP19, ZF6HP26 and ZF6HP32 are considered ZF-6 speed series Generation or version 1 transmissions. Consequently, ZF6HP21, ZF6HP28 and ZF6HP34 are considered as Generation or version 2 ZF-6 speed transmissions.
Although the computer is mounted internally on the valve body, it is good to know that solenoid location and strategy are significantly different one from another. This will help in diagnosing shift concerns in addition to viewing data in a capable scan tool.
Solenoid identification, location and strategy for the ZF6HP19 and the ZF6HP28 have notable differences. The MV1 solenoid in version 1 was eliminated in version 2. The one Normally Applied D/E solenoid (EDS4) in version 1 was changed to two solenoids Normally Vented solenoids, one for the D clutch (EDS6) and one for the E clutch (EDS4). These were the most obvious and significant differences. A more subtle difference is the only Normally Applied solenoid version 2 has is the Line Pressure Control Solenoid. Version 1 a total of 3 solenoids are Normally Applied type and 3 are Normally Vented.
