4x4 4low

I’m looking for advice on my 02 ranger edge manual transmission 3 liter, it shifts into 4x4 but not 4low. I have replaced the switch on the brake pedal and I ordered a “speed sensor “ which I installed on the rear differential. Both the 4wd lights illuminate upon starting So I am guessing there...

when i go into 4 high no probs when i try for 4 low no go :( its a 86 ranger 2.9l 5 speed manual with auto hubs and electric t case any thoughts?