Perhaps itís the same TSB as the new traverse/Acadia/enclave but well just have to see.
The Traverse, Acadia, Blazer runs the 9T65 transmission.
I think your Terrain has the 9T50 trans depending on which engine you have.
These two are similar but not the same.
I'm watching this trans issue to see how they fix it before I buy my next one.
2014 Equinox LTZ FWD 3.6L. V-6 (LFX)
GM6T70 Transmission-Gen II(M7W)
Crystal Red Tintcoat-Brownstone Leather-(FE2) Suspension-18" Wheels
Build Date: Nov. 04, 2013-Delivery Date: Nov. 25, 2013