Hello. I have a 1988 cevrolet celebrity 2.8.1 automatic transmission 4t60. after a complete repair, I did not have front speed. I found the reason. 1-2 servo assembly piston seal was broken. after repair, there was a forward movement in all d1 d2 d3 d4 though only at the first speed. does not switch from the first to 2 and 3-4