2000 freightliner auto shift not revving up over 1600, no shift

I have a 2000 freightliner century class, started only revving to 1600rpm, won't up shift- stays in 2nd. when you start it up, i can rev it up normally, then it will drop down to 1600, and top out there. (in neutral, in reverse, in drive.) what is going on??

took ecm and had it tested, they said was good.
cleaned ecm connections

 

HOW DO I PULL CODES?
what is the shaker? It has Eaton-fuller Trans, auto shift w/clutch - does have dash computer, i think . . it's got the buttons to record events, ect. By the way what is the purpose/how do these work?

Did some more diagnosing yesterday, found speedometer not moving, going to try replacing VSS. (speed sensor on tail of TRANS.)

Somthing else too: when you start the truck, as i'd mentioned in first post, you can revv the engine up to about 2000rpm, then in about 20-30sec it will cut it down to 1600rpm. Thinking that the lower RPMs was why it wasn't shifting, i started it real quick, and got it in gear, gunnning it to see if it would shift before the RPMs cut down. It didn' really want to shift even then,acted like it didn't know when to shift, had to pulse the accelerator to get it to lock in.

Is it normal to be able to start off in all the gears? I is letting me select up to 6th gear, and letting off the clutch, will engage in that gear.

 

Ok, Replaced the VSS . . still not working. I ended up pulling the batt. cables to reset the codes, it actually shifted and revved just fine for aprox. 5min, then the check engine light came on, followed by the wheel spin light. . . no shift again, no speedometer, no revv over 1600. (did this several times, got the same resultes each time)

Help!!