According to the manual for that transmission (RL4R01A) it has 8 items that I'll list in order:
- Oil Level and Quality
- Line Pressure
- Governor Pressure
- Throttle Wire
- Over Drive Switch and Wiring
- Over Drive Cancel Solenoid
- Control Valve
- Governor Valve
You need to get the manual for the transmission if you plan on trying to fix it yourself. I recommend the ATSG manual. You can pick it up on line if you can not find it local. I called a couple independant parts stores before I got mine. I hope you don't have the same problem I have. I also bought mine used and it appears that someone decided that the tranmission could do without a couple control valves (1-2 and 3-4). It shifts from 1st to 3rd and fails to go into 4th. The only time it will go into 2nd is if I start out with the shifter in 2nd. Then it will take forever to shift into 2nd.
Good Luck, Leo
> >>Nissan 1997 pickup, bought used, 4-cyl fuel injected engine,
> >>4-speed automatic, 56,000 miles (very likely actual mileage
>
> >> Starting a few days ago, my 4-speed automatic sometimes won't
> >>shift into 3rd or 4th but instead stays in 1st and 2nd. When
> >>it does this, it shifts into 2nd at almost exactly 4,000 RPM,
> >>whether the acceleration is hard or gentle. The shifts have
> >>felt normal, both when the problem occurs and when it does not. > >>
> >>No OBD II codes, oxygen sensor test shows about 50% duty cycle
> >>(built-in test), and I feel that the transmission itself is
> >>OK but that there's something wrong with a sensor or electrical
> >>cable, especially the latter since apparently the engine was
> >>once removed and the cables weren't reinstalled quite right
> >>(transmission cables run on wrong side of filler pipe, cable
> >>hangers left dangling).
> >>
> >>What component, outside of the transmission, can make it
> >>stop shifting into 3rd and 4th?
>
> > Speed sensor. Is the speedometer working?
>
> Speedometer is working, and it's an electric one, as opposed to the
> mechanical type. But the speed sensor, at the end of the transmission
> and connected through one of the dangling cables, seems to connect
> only to the speedometer and not the computer. I haven't been able to
> get a wiring diagram for the transmission.