Thomaslipe

I have a 1992 LS 400 and it shifts directly from 1st to 3rd gear. When it is cold it actually aways shifts great but after driving it for about 15 minutes it starts going from 1st to 3rd which gives a big power lug when accelerating. I can shift it back to 2nd manually without any problem and then shift back to 3rd once i am up to speed. It also won't downshift back to 2nd when you try and accelerate. again i can manually downshift fine. If i am slow enough it will downshift to 1st gear. The Lexus dealer changed the trans oil when i bought it about 10 months ago so it should have the correct fluid. I since had the trunk hinge wire issue fixed so that is not part of this problem. It's been doing this all along. It is annoying but it really shifts smoothly and runs great otherwise. Haven't found this same problem on any posts. Can someone five me some direction.