The car has 140,000 miles. rebuilt transmission at 110K. I had it in for a trans service at 137K, they also fixed a vacuum problem, now it slip when it shifts, not always, mostly under full throttle. I have been told that the modulator on the transmission can be adjusted. How do I do this. I don't want to bring it back to the shop that did it, as they just want to rebuild this transmission, eventhough it only has 30K on it....