I have an Airtronics RD6000 Tx and an Airtronics 92765 Rx and am using identical Airtronics servos. For the first time, I am trying to set up a split elevator system. Following the manual directions, I first restored all factory defaults. Then I slaved the gear channel (Aux.) to the elevator channel. After I dialed in some up and down differential, the two servos operate "together," but not equally--not even close. If I try to adjust the difference mechanically (linkage, clevis hole), the neutral is off and the throws do not match, either. If someone knows what I am doing wrong, I would appreciate a word of advice. If not, I'll just go with the other alternative of a Y harness. Thank you for reading this far, Dzl

Take out the differential.
Set the endpoints on each channel the same.
Set the neutrals on both servos with trims at zero, power on, surfaces at neutral, using the adjustments on the pushrods. Don't do anything electrical, or offsetting the servo arms on each servo. This will introduce differential, which you don't want.
Then do the other stuff... setting rates, expo...

Thanks a bunch. I did what you suggested, and also changed over to the other Aux. channel for setup and now it works. I should have posted here yesterday before I spent a frustrating hour and a half trying to "hack" my way through the problem. Appreciatively, Dzl