Review on AGFRC Sub-Micro Servo Motor - Upgrade Metal Case Titanium Gear 4.5Kg HV Mini Servo For 1/14 1/18 1/24 RC Cars Planes (B13DLM V2) by Judy Lawrence

This servo is a beast. 100% great action for a shift servo. Has plenty of torque. Not an aircraft guy but I bet this is for the money the best you could get. Now in order to use this as a shift servo you have to modify the bracket as it's about 5mm deeper on the Summit/Revo this is doable leaving a small gap at the top and enough material on the bottom for it to remain rigid. I haven't looked at what it would take to install it on a Trx4 but if you're good with modifications I bet you could make it work. The other consideration is the servo horn spine is smaller than the 2056 so you'll have to use the included servo horns. Which are not spring loaded so you may want to buy a servo saver if you use it for the diff locks or the shift on a Trx4.