On Wednesday, May 8, 2019 at 8:36:37 PM UTC-7, wrote:
I have a trig transponder (no ADSB yet). This transponder is not legally required in a glider. So, do I still have to get the transponder checked every two years per 91.413?

https://www.law.cornell.edu/cfr/text/14/91.413

It appears so to me, but am I missing something?

Yes, there is no difference here between gliders (and other transponder partial exemption aircraft) and a VFR powered aircraft. It is clear in the regulations.