Why is there a vibration at 25 miles after transmission has gone through gears. Is the converter bad?

Hello, 25 miles per hour is not typically when you would expect engagement of the torque converter necessarily. It seems a little early. That said, a diagnostic tool can monitor operation of shift solenoids as well as torque converter clutch engagement, and should also be able to monitor if such components cause a shudder. How many miles are on your Equinox? What kind of testing has been performed so far? Are there any trouble codes set in the engine's processor? I'd recommend having testing performed to see if you have any clues before anything else. https://repairpal.com/auto-repair-near-me