Dont worry about any slip numbers that are not in the top of high gear, max RPM. Otherwise its just not accurate data. Here is a screen pic of one of the runs in the Vette 8.01 170.. The red line is engine RPM, the green line is driveshaft RPM, yellow is accel G's It is slipping 9% at the stripe. Don't read a ton into converter efficiency IMO we have been as fast at 10% as we have been at 1% overdrive with more power after making changes last year to a lock up converter. This year is a new pump design, gearset, and new stators from this. We shall see if we can make the lockup deal run faster than the slipping stuff, but so far not happened. I have often found "less efficient" converters to be faster than super tight efficient ones.