Dr.Godzilla

I joined the forum just to post my resolution to the vibration issue. Background: 2015 Yukon XL 4WD with a 5.3 and 6 speed transmission. 167k miles. The truck would violently vibrate over 75mph to a point of it being scary. Vehicle was religiously maintained at the GMC dealer its entire life with regular fluid changes and maintenance. Issue: As to the vibration, I have tried every solution in the 857 pages of this thread including new tires, balancing, new trans cooler and lines in the TSB above, flushed transmission several times, new filters, etc and nothing worked. Solution: In the end, a reman transmission from GM installed at the dealer solved all vibration issues. GM = trash.