My EF fairmont V8 is eating the C4 clutch packs in the auto.

I've rebuilt he transmission and now have removed the transmission for the second time as it was quite right and have pulled it apart only to discover it ate the C4 clutch pack again.

The S1 solenoid (opens/closes the 3-4 shift valve that feeds the C4 clutch pack) does not measure outside of the allowable resistance range when checked with a multimeter.

Does any one know what voltage the solenoid is so i can check it's operation?

Or does any one know what else may be causing the trans to eat the C4 clutch packs?