Help diagnosing my ABS issue

I drive a 1995 BMW 325i (automatic tranny) and I am having some issues I need help with (this is my first BMW). My ABS light stays on, sometimes my tach won't work but most of the time it will, and my transmission shifts very late like it almost won't shift. If I put it into manual mode it shifts great. It is not slipping at all its just that it shifts very late often (sometimes it shifts perfect.) I'm a ford guy and it feels very similar to a bad modulator or very late shift points. I did a little research and I'm confused where to start diagnosing. Should I start with the wheel speed sensors or the speed sensor on the differential or something else? If I should start with the wheel speed sensors is the specific one to start with that controls those components I'm having issues with? Thanks for any help or advice you can provide.