My car is hesitatating and jerking

If you start the engine and just rev it up in neutral what does it do? Does it still buck and jerk or is it smooth. From the description it sounds like it could be internal to the transmission. Is the check engine light on or flashing during the times it is jerking?

Here is a test procedure to get the code from the trans control unit.

95-97 Nissan
1. Start engine and warm to normal operating temp with O/D off.
2. Turn ignition switch to OFF position wait 5 sec.
3. Turn ignition switch to the ACC position.
4. Switch O/D to ON.
5. With shifter in Park, turn ignition ON but don't start engine.
6. The OD light should come on for about 2 secs.
6A- If light DOES NOT come on the transmission control computer has failed.
6B. If light comes on proceed to number 7.
7. Turn ignition key to OFF.
8. Turn ignition key to ON, don't start engine.
9. Move shift lever to Drive, turn ignition key to OFF.
10. Put O/D switch to off position.
11. Turn ignition off.
12. Put O/D to off, turn ignition ON wait 2sec and move shifter to the 2 position.
13. Put O/D to on, move shifter to 1 position.
14. Put O/D to off, depress accelerator all the way to floor and release.
15. The computer is now in output mode and will start displaying the codes.

There’s one long flash that signifies the start of the sequence.
Following should be 10 short flashes. Then it repeats.

Now from that first long flash start counting the flashes. You are looking for one or more LONG flashes. The long flashes signify a code based on the following table.

All 10 flashes the same = No error codes read at this time

1st flash longer = Revolution sensor is shorted or disconnected.
2nd flash longer = Speed sensor circuit is shorted or disconnected.
3rd flash longer = Throttle sensor circuit is shorted or disconnected.
4th flash longer = Shift solenoid “A” circuit is shorted or disconnected
5th flash longer = Shift solenoid “B” circuit is shorted or disconnected
6th flash longer = Overrun clutch solenoid circuit is shorted or disconnected
7th flash longer = Lock-up solenoid circuit is shorted or disconnected
8th flash longer = Fluid temperature sensor is disconnected or A/T control unit power source circuit is damaged.
9th flash longer = Engine revolution signal circuit is shorted or disconnected
10th flash longer = Line pressure solenoid circuit is shorted or disconnected

If the flashes are all the same but there was no long start flash = Battery low, been disconnected, or control unit has just been reconnected.

Or connect a scan tool up that can read the codes and information stored in the transmission control unit. Pleas return with the results and we can continue.

Check to see if the joint is the correct one, I have seen a couple times where the parts looked okay but were not correct. The splines would slip internally.

If it does not rev in neutral you have an issue with the engine as well as the transmission. I would check over any connections or wiring around the axle area as well, It is possible you have something shorted.