I have a 93 Jimmy with 176,00, 4.3L vortex, 2WD, when trying to pass, it does not downshift, the engine revs up, but the Jimmy just seems to lose power. If I back out of it, then accelerate slowly every thing seems OK. Fluid is good and was changed about 10,000 miles ago. I have tried it in drive and overdrive, seems like 2nd gear is Ok if I drive it with 2nd selected.