'96 960 only stay in first gear

[whitebulldog73]

hello all,

Im new to this forum, but alot like most have a car problem they just cant figure out. My problem is in the transmission, it wont upshift, even if i manual shift the automatic. i recently flushed the tranny with new fluid,an filter. The car was neglected in the operating part of it before i got my hands on it. I had a problem soon after i bought it, the fluid was over due to be changed, the car wouldn't move at all. After i changed the fluid, the car ran great, like it should, but then i was shifting in an out of overdrive, an stumbling going into 2nd gear. Now, it brings us up to date, the weekend after i flushed the tranny, i wouldn't upshift. I first thought of the PNP switch, but now im hooked on being a bad of faulty rear axle speed sensor.